3 syllables:
skillfully, visibly, timpani, symphony, synchrony, visually, tiffany, tinselly, whiffletree, infamy, flippancy, stringency, sympathy, viciously, wicopy, timothy, willowy, stickily, dimity, dittany, signally, wiggly, ministry, fixity, fidgety, instantly, vividly, filigree, brilliancy, litany, spitefully, symmetry, trilogy, brilliantly, stingily, finicky, trinity, brittany, imagery, instancy, villainy, bigotry, dismally, fiscally, wilfully, flippantly, bigamy, dingily, mistily, rickety, dignity, willfully, tripoli, whippletree, differently, finitely, timidly, minutely, sicily, swingletree, infancy, piquancy, italy, syncope, chivalry, infantry, giddily, dizzily, bishopry, chintzily, filthily, flindosy, frigidly, hymnody, licitly, lingually, millime, minstrelsy, pipal tree, prissily, quizzically, ribbony, shittah tree, simile, skilfully, stringently, trickily, twinkly, viscidly, windily, winsomely, wriggly

4 syllables:
polygyny, proclivity, sufficiently, futility, viscidity, magistracy, benignancy, proficiency, facsimile, hostility, captivity, vicinity, gravimetry, torridity, indignity, salinity, antiquity, malignancy, publicity, invisibly, contingency, auspiciously, virility, utility, implicitly, solidity, resiliency, rigidity, liquidity, acidity, obstinately, rapidity, perniciously, tumidity, vapidity, aridity, astringency, toxicity, fluidity, humidity, timidity, turbidity, fragility, civility, antistrophe, ambitiously, affinity, antipathy, deficiency, spasticity, officially, cyclicity, initially, fertility, complicity, delinquency, sapidity, sweet cicely, asynchrony, polyphony, senility, deliciously, infinity, torpidity, epiphany, soliloquy, docility, ability, simplicity, religiously, flaccidity, abysmally, pasigraphy, miserably, polygamy, tepidity, proximity, avidity, limpidity, felicity, antigone, sufficiency, explicitly, turgidity, festivity, placidity, literally, activity, immorally, consistently, liberally, tonicity, validity, mobility, prolixity, amphictyony, sphericity, culicidae, agility, somniloquy, viridity, nobility, ductility, asymmetry, consistency, propitiously, morbidity, efficiency, debility, divinity, nativity, epitome, efficiently, calligraphy, exigency, irritably, acclivity, acridity, blessed trinity, declivity, forgivably, gelidity, insistency, malignity, mendicancy, motivity, permissibly, persistency, persnickety, plasticity, propinquity, put differently, rusticity, sanguinity, stolidity, tactility, unthinkably, ventriloquy, with sympathy

5 syllables:
intermittency, self-sufficiency, cucurbitaceae, alkalimetry, expeditiously, inauspiciously, exiguity, insufficiency, contractility, eccentricity, insufficiently, conditionally, relativity, creativity, unofficially, alkalinity, surreptitiously, masculinity, meretriciously, inefficiency, atonicity, originally, pellucidity, probability, supersymmetry, elasticity, domesticity, artificially, conductivity, injudiciously, volatility, holy trinity, deliberately, magnanimity, ellipticity, legibility, negativity, versatility, invalidity, infelicity, peripherally, catholicity, additionally, electricity, insipidity, intrepidity, femininity, inutility, calorimetry, feasibility, aborigine, inconsistency, chromaticity, unanimity, promiscuously, viability, fortuitously, traditionally, flexibility, possibility, productivity, irresistibly, inefficiently, unchristianly, specificity, avariciously, reactivity, colorimetry, capability, selectivity, absorptivity, chondrodystrophy, concentricity, consanguinity, expansivity, granadilla tree, imbecility, impermissibly, inconsistently, inhospitably, mass deficiency, mental imagery, mirror symmetry, mutability, notability, perceptivity, progressivity, quotability, reflectivity, refractivity, reluctivity, resistivity, retentivity, risibility, sapodilla tree, sex activity, stretchability, syllabicity, tangibility, taoist trinity, transitivity, unambitiously, unforgivably, unpredictably, unpropitiously, without sympathy, with efficiency, with hostility, with validity, zinc deficiency

6 syllables:
compatibility, radial symmetry, idiosyncrasy, invisibility, superciliously, susceptibility, reliability, individually, amiability, unequivocally, periodicity, muscular dystrophy, availability, malleability, apocynaceae, perfectibility, joint probability, acceptability, mental deficiency, neuropsychiatry, responsibility, public utility, applicability, pusillanimity, irritability, adaptability, palatability, unconditionally, admissibility, insensitivity, ignominiously, amicability, analyticity, antifertility, approachability, business activity, commutability, compressibility, contemptibility, correlativity, deductibility, despicability, digestibility, duplicability, equatability, excitability, higgledy-piggledy, human activity, illegibility, immutability, impeachability, implausibility, improbability, incapability, inelasticity, infeasibility, inscrutability, insensibility, intangibility, intransitivity, latent hostility, learning ability, mental ability, perceptibility, permutability, practicability, reputability, reversibility, semifluidity, social activity, suggestibility, unfeasibility, unsuitability

7 syllables:
superconductivity, juvenile delinquency, inaccessibility, sexual activity, relative humidity, bioelectricity, bilateral symmetry, anthropocentricity, comprehensibility, hydroelectricity, irresponsibility, radioactivity, lactobacillaceae, static electricity, photoconductivity, special relativity, thermoelectricity, capital of italy, commercial activity, current electricity, disreputability, doctor of divinity, imperceptibility, imperishability, imperturbability, impracticability, inadmissibility, inapplicability, incommutability, incompressibility, inconvertibility, indigestibility, indisputability, ineligibility, intelligibility, in all probability, irrepressibility, irreversibility, magical ability, master of divinity, natural ability, offensive activity, physical ability, radial asymmetry, reprehensibility, sensory activity, substitutability, subversive activity, unacceptability, unadaptability, unapproachability, unpalatability, unsusceptibility

8 syllables:
theory of relativity, general relativity, piezoelectricity, australian aborigine, bachelor of divinity, civic responsibility, dynamic electricity, indistinguishability, intelligence activity, irrational hostility, performance capability, sense of responsibility, unintelligibility

9 syllables:
atmospheric electricity, educational activity, military capability, operating capability

10 syllables:
coefficient of elasticity, conservation of electricity, extracurricular activity, special theory of relativity, without showing responsibility

11 syllables:
general theory of relativity