[n] a change downward; "there was a sharp drop-off in sales"
[n] a steep high face of rock; "he stood on a high cliff overlooking the town"; "a steep drop"
[n] a noticeable decline in performance; "the team went into a slump"; "a sudden slack in output"; "a drop-off in attendance"; "a falloff in automobile sales"
[v] change from a waking to a sleeping state; "he always falls asleep during lectures"
[v] fall or diminish; "The number of students in this course dropped off after the first test"
[v] get worse; "My grades are slipping"
cliff, decrease, dope off, doze off, drift off, drop, drop away, drowse off, fall asleep, fall away, fall back, fall behind, falling off, falloff, flake out, lessening, lose, nod off, recede, slack, slip, slump
advance, arouse, awake, awaken, come alive, gain, gain ground, get ahead, increase, make headway, pull ahead, wake, wake up, waken, win