drop off

verbs

fall or diminish
"The number of students in this course dropped off after the first test"
drop off
is derived from
drop-off
is a type of (narrower)
decrease in size, extent, or range
"The amount of homework decreased towards the end of the semester"; "The cabin pressure fell dramatically"; "her weight fell to under a hundred pounds"; "his voice fell to a whisper"
decrease, diminish, fall, lessen
change from a waking to a sleeping state
"he always falls asleep during lectures"
dope off, doze off, drift off, drop off, drowse off, fall asleep, flake out, nod off
leave or unload
"unload the cargo"; "drop off the passengers at the hotel"
discharge, drop, drop off, put down, set down, unload
retreat
drop off, fall back, fall behind, lose, recede
get worse
"My grades are slipping"
drop away, drop off, fall away, slip
is derived from
drop-off