Definition of "decelerate"
verb
third-person singular simple present decelerates, present participle decelerating, simple past and past participle decelerated
(intransitive) To go slower.
Quotations
One of the disadvantages of increasing intermediate stops is that, as we have pointed out already, certain prestige trains have to suffer, notably the "Cornish Riviera Express", slowed 15min to Plymouth by stops at Taunton and Exeter; the "Torbay Express", decelerated 18min by stops at Reading, Westbury, Taunton and Newton Abbot; and the "Bristolian", which adds 14min in order to allow for a Bath stop and an increased load.
1961 October, “The winter timetables of British Railways: Western Region”, in Trains Illustrated, page 590