blast 1. vt.,n. Synonym for BLT, used esp. for large data sends over a network or comm line. Opposite of snarf. Usage: uncommon. The variant `blat' has been reported. 2. vt. [HP/Apollo] Synonymous with nuke (sense 3). Sometimes the message `Unable to kill all processes. Blast them (y/n)?' would appear in the command window upon logout.