implosion

n. [ Formed by substitution of pref. im- in for pref. ex- in explosion. ] 1. A bursting inwards, as of a vessel from which the air has been exhausted; -- contrasted with explosion. [ 1913 Webster ]

2. Hence: The inward-moving detonation wave cause by detonation of explosives arrayed spherically around a core; -- a technique used in atomic bombs to compress fissionable material to allow a chain reaction time to produce an explosion of the fissionable material. [ PJC ]

3. (Phon.) A sudden compression of the air in the mouth, simultaneously with and affecting the sound made by the closure of the organs in uttering p, t, or k, at the end of a syllable (see Guide to Pronunciation, §§159, 189); also, a similar compression made by an upward thrust of the larynx without any accompanying explosive action, as in the peculiar sound of b, d, and g, heard in Southern Germany. H. Sweet. [ 1913 Webster ]