It can mean two things. It occupies the number a trillion place in an immense listing or also that is only an infinitesimal part of a whole that has a trillion parts.
THREETHS the trillotyth of a unit . A part of the 1. 000 . 000 . 000 . 000 . 000 . 000 ( 1/10*12 or 10*-12 ) ) of parts in which a unit is divided .