drop off (
http://definr.com/drop off)
v 1: fall or diminish; "The number of students in this course
dropped off after the first test"
2: change from a waking to a sleeping state; "he always falls
asleep during lectures" [syn:
fall asleep,
dope off, {flake
out},
drift off,
nod off,
doze off,
drowse off]
[ant:
wake up]
3: retreat [syn:
fall back,
lose,
fall behind,
recede]
[ant:
gain]
4: get worse; "My grades are slipping" [syn:
slip,
drop away,
fall away]