knotty, prickly, vexing, contentious, nettlesome, touchy, ticklish, intractable, weighty, unresolved, tricky, delicate, complicated, irresolvable, sticky, dicey, controversial, problematic, hot potato, troublesome, fractious, divisive, daunting, perplexing, festering, tortuous, messy, unresolvable, problematical, unsolvable, murky, insolvable, convoluted, testy, rocky, neuralgic, complex, insoluble, bog, tangled, difficult, intriguing, abstruse, awkward, unsettled, philosophical, unpalatable, unpopular, stumbling block, byzantine, resolvable, discussable, acrimonious, arduous, elusive, germane, emotive, arcane, sensitive, straightforward, meaty, myriad, lingering, rancorous, fernlike, esoteric, disputable, unwieldy, perilous, pettier, bristly, nuanced, muddled, recalcitrant, challenging, surmountable, perennial, toothsome, nagging, sticky wicket, bramble, tempestuous, tactful, unforthcoming, bumpy, tough, nebulous, stormy, irksome, ambiguous, unwieldly, untangled, debatable, laborious, tantalizing, tedious, variegated, tractable, pertinent, simultaneous equations, bewildering, protracted, arable, carts, common, concur, dependant, fair, hoes, hundreds, longs, mountainous, oaken, ploughs, renders, solitary, tallies, tell, wooden, \u00ab, \u2122, adept, thorn, leafless, shrubby, leafy, matted, scrubby, thorniest, laurel, hazel, stunted, chaparral, deciduous, leafed, luxuriant, thornless

acacia farnesiana, acanthocyte, blackthorn, black locust, bramble, brier, buckthorn family, bumelia lycioides, caesalpinia decapetala, caesalpinia sepiaria, camachile, cassie, chaenomeles japonica, chaenomeles speciosa, chanal, chanar, christ's-thorn, citron, citron tree, citrus, citrus medica, citrus tree, crataegus, crataegus laevigata, crataegus oxycantha, english hawthorn, erythrina indica, erythrina variegata, family rhamnaceae, firethorn, fire thorn, flame tree, genus crataegus, genus paliurus, genus pisonia, genus pithecellobium, genus pithecolobium, genus poterium, genus pyracantha, geoffroea decorticans, honey mesquite, huamachil, huisache, indian coral tree, japanese quince, japonica, jerusalem thorn, manila tamarind, maule's quince, may, mimosa bush, mock orange, mysore thorn, paliurus, paliurus spina-christi, paloverde, pisonia, pithecellobium, pithecellobium dulce, pithecolobium, poterium, prosopis glandulosa, prunus spinosa, pyracanth, pyracantha, rhamnaceae, robinia pseudoacacia, scented wattle, shittim, shittimwood, sloe, southern buckthorn, sweet acacia, sweet wattle, western honey mesquite, whitethorn, wild tamarind, yellow locust

armed, barbed, barbellate, briary, briery, bristled, bristly, burred, burry, difficult, hard, prickly, spiny