I'm an engineer and the term is used often in speaking and writing.
In calculations and proofs, acceleration is always used.
The reason 'deceleration' is used in scientific writing is that it is the most concise way of communicating the idea at hand.
Some engineers and physicists are pedantic asshats and will not use that and similar terms, but that is an incredible mistake. Most of engineering writing is not for other engineers, it is for the less technical public. Almost all of my writing in my career has been to communicate ideas to managers, and purchasing agents; or as manuals for multi-million dollar machines so machinists could operate them. I'm not going to talk about 'negative acceleration', I'll use 'deceleration', or even, *gasp*, 'slows down'.
Technical writing is not to prove how smart you are, it is to convey ideas in the most precise, concise, and understandable way possible.