weaken

v.

1. To become weaker

   lessen, lose, decrease, relapse, soften, relax, droop, fail, wane, crumble, halt, limp, languish, fade, decline, abate, totter, tremble, flag, faint, wilt, lose spirit, become disheartened, fail in courage, slow down, break up, crack up*, wash out*.

   Antonyms revive*, strengthen*, straighten. *

2. To make weaker

   reduce, minimize, enervate, debilitate, exhaust, cripple, unman, emasculate, castrate, devitalize, undermine, impair, sap, enfeeble, unnerve, incapacitate, impoverish, thin, dilute, take the wind out of*, wash up*; see also decrease 2.

   Antonyms revive*, quicken*, animate.

weaken, the most general of these words, implies a lessening of strength, power, soundness, etc. weakened by disease, to weaken an argument; debilitate suggests a partial or temporary gradual weakening, as by disease or dissipation debilitated by alcoholic excesses; enervate implies a lessening of force, vigor, energy, etc., as through indulgence in luxury enervated by idleness; undermine and sap both suggest a weakening or impairing by subtle or stealthy means authority undermined by rumors, strength sapped by disease