Real Dictionary

aspirate in American English
to begin (a word) or precede (a sonorous speech sound) with a puff of breath resulting in the sound (h)
adjective: pronounced with or accompanied by aspiration; aspirated
noun: a speech sound having as an obvious concomitant an audible puff of breath, as initial stop consonants or initial h-sounds
transitive verb: to articulate (a speech sound, esp. a stop) so as to produce an audible puff of breath, as with the first t of total, the second t being unaspirated

aspirate in British English
noun: a stop pronounced with an audible release of breath
verb: to articulate (a stop) with some force, so that breath escapes with audible friction as the stop is released