"Slow downs" refers to a decrease or reduction in the speed or pace of something. It means things are not moving as quickly as they usually do. Full definition
There are however occasional slow downs when there is a lot happening on screen and it is especially noticeable when playing the two player co-op mode. (gamergeddon.com)
While it is in the air you might want to do some normal startups and slow downs as well. (mechanics.stackexchange.com)
They merely cause temporary slow downs or speeding up of surface temperature warming. (skepticalscience.com)