When things quicken, they speed up or make something go faster. If you’re late for school, you should probably quicken your pace.
Your heartbeat probably quickens when you’re afraid or after you’ve been running fast, and you could also say that your curiosity quickens (or increases) when you overhear a mysterious phone call. The oldest meaning of quicken, however, is “come to life,” a definition which sounds very old fashioned now, but which was once used to describe an advanced stage of pregnancy: “The fetus began to quicken.”
make keen or more acute
give life or energy to
give new life or energy to
show signs of life