Drop around
Visit someone, often without making an arrangement
Drop away
Become smaller- amount, numbers
Drop back
Move towards the back of a group
Drop behind
Move towards the back, not keep up
Drop by
Pay a brief visit; To visit someone informally.
Drop in
Visit without having made arrangements
Drop off
Take something or someone to a place and leave it or them there.
Drop out
Quit a course
Drop over
Visit for a short time
Drop round
Visit someone, often without making an arrangement
Drop someone in it
Get someone into trouble
Drop through
Come to nothing, produce no results