is a specific kind of: deepen, intensify.

is a broader term that covers: brisk, brisk up, brisken.

is the opposite of: decelerate, retard, slow, slow down, slow up.

derivation: hurrying, speed, speeding | acceleration, quickening, speedup | fastness, speed, swiftness | speed, velocity | accelerative, acceleratory.

is a specific kind of: alter, change, modify.

is the opposite of: decelerate, slow down.

derivation: hurrying, speed, speeding | acceleration, quickening, speedup | accelerator, throttle, throttle valve | accelerator, accelerator pedal, gas, gas pedal, gun, throttle | fastness, speed, swiftness | acceleration | speed, velocity | accelerative, acceleratory.