Meaning : Fall or diminish.
Example :
The number of students in this course dropped off after the first test.
Meaning : Change from a waking to a sleeping state.
Example :
He always falls asleep during lectures.
Synonyms : dope off, doze off, drift off, drowse off, fall asleep, flake out, nod off
Meaning : Retreat.
Synonyms : fall back, fall behind, recede
Obtain advantages, such as points, etc..
The home team was gaining ground.