perplexing, thorny, intractable, nettlesome, knotty, troublesome, puzzling, problematic, daunting, baffling, trickiest, troubling, touchy, contentious, irksome, unsolvable, ticklish, exasperating, irresolvable, unresolved, insolvable, mystifying, complicated, maddening, prickly, intriguing, nagging, bothersome, solvable, insoluble, problematical, worrisome, solving, stickiest, dicey, serious, unanswerable, weighty, festering, elusive, unsettling, bewildering, imponderable, salient, peculiar, unappetizing, frustrating, glaring, tantalizing, simultaneous equations, unpalatable, persistent, difficult, inconvenient, disconcerting, lingering, complex, pertinent, challenging, pesky, costly, paradoxical, perilous, inscrutable, infuriating, myriad, recalcitrant, germane, important, interesting, esoteric, confusing, murkiest, sticky wicket, galling, discomforting, fascinating, controversial, gravest, dispiriting, afflicting, unresolvable, surmountable, divisive, unnerving, convoluted, neuralgic, rankling, obvious, tractable, simplest, disquieting, insuperable, stumbling block, irritating, messy, unappealing, existential, abstruse, perennial, debatable, resolvable, particular, permeable, wavering, absorbent, absorbing, acrimony, admits, ado, advan, advanced, alarm, alienating, americanized, annoyance, anxiety, anyone, apropos, arousing, ascetic, astray, unsolved, tricky, embarrassing, trickier, vexatious, distressing

mocking, quizzical, teasing, vex

annoying, bothersome, disagreeable, displeasing, exasperating, galling, infuriating, irritating, maddening, nettlesome, pesky, pestering, pestiferous, plaguey, plaguy, teasing, vexatious