Synonyms and related words :
Chinese puzzle, adherent, adhesive, baffling problem, barnacle, billhead, book stamp, bookplate, brain twister, bramble, brand, brier, bristle, broad arrow, bulldog, burr, cachet, cactus, catchweed, cement, check, cleavers, colophon, counterfoil, countermark, crossword puzzle, crux, decal, decalcomania, docket, enigma, enigmatic question, floorer, glue, goose grass, government mark, government stamp, gunk, hallmark, imprint, jigsaw puzzle, knot, knotty point, label, leech, letterhead, limpet, logo, logotype, masthead, mind-boggler, molasses, mucilage, mystery, needle, nettle, nut to crack, paste, perplexed question, perplexity, pine needle, plaster, plate, poser, price tag, prickle, problem, puzzle, puzzlement, puzzler, question, question mark, quill, registered trademark, remora, running head, running title, seal, sigil, signet, sixty-four dollar question, spicule, spiculum, spike, spikelet, spine, stamp, stub, stumper, syrup, tag, tally, thistle, thorn, ticket, title page, token, tough proposition, trade name, trademark, trademark name, vexed question, why, yucca