Weaken

1. v. i. To become weak or weaker; to lose strength, spirit, or determination; to become less positive or resolute; as, the patient weakened; the witness weakened on cross-examination.
2. v. t. To make weak; to lessen the strength of; to deprive of strength; to debilitate; to enfeeble; to enervate; as, to weaken the body or the mind; to weaken the hands of a magistrate; to weaken the force of an objection or an argument.
3. v. t. To reduce in quality, strength, or spirit; as, to weaken tea; to weaken any solution or decoction.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.