weaken, v. 1. enfeeble, debilitate, enervate, devitalize; exhaust, deplete, sap, impoverish; tire, strain, fatigue, Inf. take it out of [s.o.], unnerve, unman, emasculate, effeminize.
2. impair, invalidate, incapacitate, cripple, handicap, undermine; dilute, adulterate, debase, water, water down, Inf. cut; thin, attenuate; lessen, diminish, lower, reduce, minimize.
3. tire, languish, fail, fade, decline; wane, droop, faint, flag, drop; totter, shake, dodder, crumble; (all usu. of health) lose ground, take a turn for the worse, go downhill; (all usu. of psychological or emotional health) crack, let go, break down, come apart at the seams.
4. relent, give in, acquiesce, yield, give way, bend, soften; accede, agree, assent, consent, concur, Inf. come round; relax, ease up, let up.
weakling, n. featherweight, Inf. lightweight, baby, small fry; loser, Walter Mitty, SI. sad sack, SI. doormat, SI. pushover, SI. patsy, SI. schnook, SI. easy mark; Inf. jellyfish, SI. nebbish, SI. weak sister, SI. weak stick, SI. schlepp, SI. schlemiel; namby-pamby, milquetoast, milksop, sop, mollycoddle, mother's or mama's boy, Little Lord Fauntleroy, SI. sap, SI. wimp, SI. twirp, SI. nerd, SI. twit; softy, sissy, effeminate, woman, Inf. pantywaist, SI. cream puff, SI. pansy, SI. wimp, SI. old woman; big baby, crybaby, mouse, SI. fraidy-cat, SI. scaredy-cat; coward, poltroon, Archaic. caitiff, dastard, Inf. chicken.
weakness, n. 1. feebleness, puniness, frailty, frailness, fragility, fragileness, delicateness, delicacy; impotence, impuissance, powerlessness, helplessness, incapacity, inability, incapability, ineptness, ineptitude; exhaustion, enervation, lack of strength, anemia, Pathol, adynamia, Pathol, asthenia, Pathol, neurasthenia, Pathol, atony, Pathol, atonicity; debility, infirmity, disability, valetudinarianism, unhealthfulness, invalidness, decrepitude, senility, Pathol, cachexia.
2. flaw, fault, chink or hole in one's armor, weak spot, Achilles heel, underbelly; loophole, way out, lapse, deficiency, defect, imperfection, mar, blemish, blotch, mark against [s.o.]; foible, shortcoming, failing, handicap; vulnerability, vulnerableness, liability, susceptibility, susceptibleness, openness.
3. fondness, liking, affection, love, passion, Fr. amour, fancy, appreciation, eye, taste, appetite, sweet tooth; tenderness, soft spot, special place in one's heart, partiality, preference, predisposition, leaning, inclination, proneness, propensity; penchant, desire, longing, yearning.