3 syllables:
gimmickry, whimsically, typically, filthily, fittingly, ministry, civilly, swimmingly, resignedly, trinity, imagery, hillbilly, principally, frigidly, trippingly, mimicry, wickedly, limpidly, impishly, willingly, rigidly, killingly, wittingly, realty, ceaselessly, cecity, ceiba tree, cheekily, chieftaincy, creakily, decency, decently, dreamfully, dreamily, easily, equally, evenly, frequency, frequently, genially, gleefully, greedily, heedfully, heedlessly, legally, leniency, leniently, needfully, peaceably, peacefully, piquancy, piquantly, readably, recency, recently, regency, screakily, seamanly, secrecy, sneakily, speedily, vis-a-vis, wheezily

4 syllables:
exquisitely, sanguinity, tranquillity, terrifically, critically, vicinity, submissively, excitingly, befittingly, admittedly, plasticity, publicity, stability, tranquility, ethnicity, liquidity, motility, cupidity, acclivity, spheniscidae, stupidity, putridity, derisively, affinity, sterility, fertility, complicity, ubiquity, motivity, scurrility, infinity, facility, linguistically, physically, declivity, simplicity, unwillingly, duplicity, cynically, lividity, obliquity, capriciously, puerility, activity, vindictively, incisively, sublimity, humility, judiciously, specifically, unwittingly, validity, servility, lucidity, indistinctly, gentility, virginity, frigidity, mobility, tactility, iniquity, gracility, acridity, stolidity, convincingly, passivity, gravidity, archdeaconry, believably, benignancy, benignantly, conceitedly, conceivably, conveniently, deceitfully, facetiously, high frequency, illegally, indecency, indecently, infrequency, infrequently, low frequency, most recently, obediently, obesity, obscenely, pass easily, serigraphy, uneasily, unequally, unevenly, unreadably, unspeakably, vehemently

5 syllables:
expansivity, refractivity, juvenility, immobility, receptivity, arability, objectivity, anonymity, absorptivity, audibility, movability, tangibility, durability, indecisively, realistically, concentricity, subjectivity, volubility, notability, suitability, portability, intrinsically, palpability, sensibility, pliability, mutability, gullibility, solubility, synchronicity, disability, affability, infertility, imbecility, unconvincingly, sociability, politically, sensitivity, transitivity, fallibility, curability, resistivity, visibility, tractability, credibility, inability, multiplicity, instability, longanimity, directivity, perceptivity, risibility, plausibility, friability, readability, unanimity, positivity, inactivity, serendipity, changeability, tenability, productivity, liability, edibility, equanimity, uncritically, culpability, authenticity, incivility, reflexivity, statistically, impassivity, acromegaly, antecedently, contumeliously, inconveniently, self-conceitedly, unachievably, unbelievably, unimpeachably

6 syllables:
admirability, compressibility, respectability, digestibility, variability, attainability, practicability, intangibility, irascibility, incredibility, predictability, tax liability, dependability, amicability, optimistically, separability, impalpability, antifertility, scientifically, inscrutability, profitability, suggestibility, impossibility, hyperactivity, serviceability, infallibility, transferability, availability, permeability, convertibility, corruptibility, navigability, invincibility, transmutability, sustainability, accessibility, vulnerability, agreeability, insensibility, intransitivity, incurability, demonstrability, inflexibility, excitability, alterability, replaceability, characteristically, dissolubility, inaudibility, contemptibility, desirability, advisability, unrealistically, adorability, commutability, reversibility, incapability, immovability, penetrability, eligibility, intractability, infeasibility, insolubility, formidability, perdurability, manageability, illegibility, destructibility, immutability, amenability, comparability, improbability, perceptibility, conceivability, unsociability, impregnability, exchangeability, absolute frequency, audio frequency, infrared frequency, medium frequency, radio frequency, relative frequency, very high frequency, very low frequency

7 syllables:
understandability, inadmissibility, inapplicability, incommutability, imperceptibility, intelligibility, incompatibility, impenetrability, inexorability, invariability, indigestibility, indestructibility, imperishability, associability, substitutability, photosensitivity, unpredictability, interchangeability, invulnerability, quantifiability, ineligibility, maneuverability, irreversibility, inevitability, reproducibility, extremely high frequency, extremely low frequency, fundamental frequency

8 syllables:
incontrovertibility, radiosensitivity, limited liability, indefatigability