drop off

definition: change from a waking to a sleeping state
example:
speech part: verb
synonyms: fall asleep
definition: fall or diminish
example:
speech part: verb
synonyms:
definition: get worse
example:
speech part: verb
synonyms: slip
definition: retreat
example:
speech part: verb
synonyms: fall back lose recede fall behind
definition: leave or unload
example:
speech part: verb
synonyms: discharge

How drop off is being used?