The Collaborative International Dictionary of English v.0.48:
Fast \Fast\, v. i. [imp. & p. p. Fasted; p. pr. & vb. n.
Fasting.] [AS. f[ae]stan; akin to D. vasten, OHG.
fast[=e]n, G. fasten, Icel. & Sw. fasta, Dan. faste, Goth.
fastan to keep, observe, fast, and prob. to E. fast firm.]
1. To abstain from food; to omit to take nourishment in whole
or in part; to go hungry.
Fasting he went to sleep, and fasting waked.
2. To practice abstinence as a religious exercise or duty; to
abstain from food voluntarily for a time, for the
mortification of the body or appetites, or as a token of
grief, or humiliation and penitence.
Thou didst fast and weep for the child. --2 Sam.
Fasting day, a fast day; a day of fasting.