(1):

(v. i.) To proceed downward, or toward a close; to decline.

(2):

(v. i.) To grow weak or faint with disappointment, grief, or like causes; to be dispirited or depressed; to languish; as, her spirits drooped.

(3):

(v. i.) To hang bending downward; to sink or hang down, as an animal, plant, etc., from physical inability or exhaustion, want of nourishment, or the like.

(4):

(v. t.) To let droop or sink.

(5):

(n.) A drooping; as, a droop of the eye.