hairline

1 being of less than usual width a hairline crack in the mug, almost too small to notice, was enough to make the mug break when filled with hot tea Synonyms fine, narrow, needlelike, paper-thin, skinny, slender, slim, slim-jim, thin, ultrathinRelated Words attenuate, attenuated, elongate (or elongated), linear; bottleneck, close, compressed, condensed, constricted, contracted, squeezed, tight, tightened; lanky, rangy, reedy, shoestring, spindly, stalky, stringy, twiggy, willowy, wispy; lank, spareNear Antonyms chunky, squat, stocky, stumpy, thick, thickset; bulky, massive, voluminous; thickish, widishAntonyms broad, fat, wide

2 made or done with extreme care and accuracy a hairline distinction between her rating of certain things as “necessary” and others as “absolutely necessary” Synonyms delicate, exact, finespun, fine, hairsplitting, minute, nice, nuanced, refined, subtleRelated Words nitpicking, quibbling; frivolous, inconsequential, inconsiderable, insignificant, negligible, petty, piddling, trifling, trivial; demanding, exacting, fastidious, finical, finicking, finicky, fussy, meticulous, particular, pickyNear Antonyms apparent, clear, clear-cut, evident, manifest, obvious, open-and-shut, palpable, patent, perspicuous, plain, transparent, unambiguous, unequivocal, unmistakable; broad, indefinite; careless, heedless, incautious, slapdash, slipshod, sloppyAntonyms coarse, inexact, rough

3 meeting the highest standard of accuracy an ultrasensitive telescope that requires hairline placement of the lenses Synonyms accurate, close, delicate, exact, fine, precise, mathematical, pinpoint, refined, rigorous, spot-onRelated Words correct, right, strict, true; definite, definitive; nice, subtle; careful, fastidious, finical, finicky, meticulousNear Antonyms approximate, round; false, incorrect, untrue, wrong; careless, loose; indefinite, unclear, vague; doubtful, dubious, questionable, unreliable, untrustworthyAntonyms coarse, imprecise, inaccurate, inexact, rough

a very small distance or degree the controversial measure passed by a hairline, the margin of victory being but a single vote Synonyms ace, hairbreadth (or hairsbreadth), hair, hop, skip, and jump, inch, neck, shouting distance, step, stone's throwRelated Words bit, crumb, dab, iota, jot, minim, mite, particle, smidgen (also smidgeon or smidgin or smidge), trace, trifleNear Antonyms infinity, light-yearAntonyms country mile, long haul, mile