#1 weaken v. lessen the strength of; "The fever weakened his body". wn
#2 weaken v. become weaker; "The prisoner's resistance weakened after seven days". wn
#3 weaken v. [sabotage, undermine, countermine, counteract, subvert] destroy property or hinder normal operations; "The Resistance sabotaged railroad operations during the war". wn
#4 weaken v. [de-escalate, step down] reduce the level or intensity or size or scope of; "de-escalate a crisis". wn
#5 weaken v. [dampen, damp, soften, break] lessen in force or effect; "soften a shock"; "break a fall". wn
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