[Skills help] trip

Syntax: trip 

Trip is a common skill used by melee fighters to knock an opponent prone.
Normally, opponents must be facing each other directly to use trip, but a reach
weapon can also be used to initiate it.  Many factors determine the success or
failure of a trip including relative size, dexterity, speed and accuracy.

You cannot trip a person who is flying.

See also: prone weapon fly