Synonyms:
- 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