haplology (n.)

A term used in PHONOLOGY, in both SYNCHRONIC and DIACHRONIC contexts, to refer to the omission of some of the sounds occurring in a sequence of similar ARTICULATIONS, as when cyclists is pronounced  , library  , etc. Some PSYCHOLINGUISTS also use the term to refer to a TONGUE-SLIP where an omission of this kind has taken place, e.g. running jump becoming rump.