One of less than average weight; [Webster 1913 Suppl.]
A person of small importance or mental ability, especially one who is unimportant but cheeky and presumptuous. [Webster 1913 Suppl.]
a wrestler who weighs 139-154 pounds. [WordNet 1.5]

lightweight, a.

Light in weight, as a coin; specif., applied to a man or animal who is a lightweight. [Webster 1913 Suppl.]
made of thin cloth, of relatively little weight; -- of clothing or fabrics; as, lightweight fabrics. [WordNet 1.5]

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OXFORD DICTIONARY

lightweight, adj. & n.
--adj.
1 (of a person, animal, garment, etc.) of below average weight.
2 of little importance or influence.
--n.
1 a lightweight person, animal, or thing.
2 a a weight in certain sports intermediate between featherweight and welterweight, in the amateur boxing scale 57-60 kg but differing for professionals, wrestlers, and weightlifters. b a sportsman of this weight.

Idiom

junior lightweight
1 a weight in professional boxing of 57.1-59 kg.
2 a professional boxer of this weight.

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THESAURUS

lightweight

Boeotian, Chinese boxer, Milquetoast, a nobody, a nothing, baby, bantam, bantamweight, banty, big baby, black belt, block, boxer, breakable, brittle, brown belt, bruiser, button, catchweight, cheap-jack, chicken, chit, cipher, clod, cobwebby, cog, common man, commonality, commonalty, creature, crumbly, crybaby, dainty, delicate, delicately weak, diminutive, dimwit, dolt, donkey, doormat, dope, dull tool, dullard, dumb cluck, dumbbell, dummy, dunce, effeminate, featherweight, fighter, figurehead, fingerling, fisticuffer, flimsy, flunky, flyweight, follower, forceless, fragile, frail, frangible, gimcrack, gimcracky, gossamery, gowk, gutless wonder, heavyweight, hoi polloi, imponderous, impotent, ineffective, ineffectual, inefficacious, inferior, insignificancy, invertebrate, jackstraw, jellyfish, jerry, jerry-built, jobbernowl, junior, karate expert, lackwit, lamebrain, light, light heavyweight, little fellow, little guy, looby, loon, lower class, lower orders, man of straw, masses, mediocrity, meek soul, middleweight, milksop, mini, minikin, minnow, minny, mollycoddle, mouse, namby-pamby, nebbish, niais, nincompoop, ninny, ninnyhammer, nitwit, no-account, nobody one knows, noddy, nonentity, nubbin, obscurity, of no account, palooka, pansy, pantywaist, papery, pasteboardy, pawn, peewee, pip-squeak, pony, powerless, prizefighter, pug, pugilist, punk, puny, pushover, put, runt, sad sack, savate expert, scrub, second fiddle, secondary, shattery, shrimp, sissified, sissy, sleazy, slight, slip, small fry, small potato, small potatoes, snip, snippet, softling, softy, sop, sparrer, squirt, squit, stupid, subaltern, subordinate, tacky, thickwit, third stringer, tit, unauthoritative, underling, understrapper, underweight, unheavy, unsubstantial, wart, weak, weak sister, weakling, weightless, welterweight, whiffet, whippersnapper, wisp, wispy, without any weight, witling, womanish, yes-man

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