'speed up' definitions:

Definition of 'speed up'

From: WordNet
verb
Move faster; "The car accelerated" [syn: accelerate, speed up, speed, quicken] [ant: decelerate, retard, slow, slow down, slow up]
verb
Cause to move faster; "He accelerated the car" [syn: accelerate, speed, speed up] [ant: decelerate, slow down]

Synonyms of 'speed up'

From: Moby Thesaurus