Isn't there a musical term for how a pianist will play a piece with 'feeling' and the tempo will get slower (usually softer) or faster (often louder) in certain parts? Piannissimo = softer?

I was playing a song I wrote on guitar and I do that on this song... it's a rather heavy duty ballad. Specifically, right after the chorus, I slow down and actually pause just a bit before starting the next verse.

Any arranger functions allow you do this decently? I mean while playing a style.