Fast

1. In a firm or secure manner, securely; in such a way as not to be moved; safe, sound [from 10th c.].

Synonyms: firmly, securely, tightlyAntonym: loosely

2. (of sleeping) Deeply or soundly [from 13th c.].

Synonym: deeplyAntonym: lightly

3. Immediately following in place or time; close, very near [from 13th c.].
4. Quickly, with great speed; within a short time [from 13th c.].

Synonyms: quickly, rapidly, speedily, swiftlyAntonym: slowly

5. Ahead of the correct time or schedule.

Synonym: aheadAntonym: behind