WordNet sense 1 (having little physical or spiritual strength):

weak

WordNet sense 2 (impaired by diminution):

diminished, lessened, vitiated

WordNet sense 3 (diminished in strength, quality, or utility):

impaired

WordNet sense 4 (reduced in strength):

attenuate, attenuated, faded, attenuate

WordNet sense 5 (made less in size or amount or degree):

decreased, reduced

WordNet sense 6 (mixed with water):

cut, thinned

WordNet sense 7 (reduced in strength or concentration or quality or purity):

dilute, diluted

WordNet sense 8 (damaged inanimate objects or their value):

hurt

WordNet sense 9 (harmed or injured or spoiled):

damaged