"Responsive" is the word describing reacting quickly and positively.
Glide would be a word that means "to move in an easy way."
Ire is a three letter word for spleen.
Cage is a four-letter word that starts with c and means cell. Or case! Or the 5 letter word Crypt!
The 6-letter word for getting bigger is "grow."
If you mean "jerk" as in the verb "to pull, move quickly, twitch," the word "vellicate" is a synonym.
to move quickly.
A three letter word for writing quickly is to jot.
"Dash" means to move quickly.
estuary
The state of matter that flows freely is liquid.
quickly
nimble the word that means to write quickly is bust to move it baby! Scribble may be the word you are thinking of.
agility
Speed
Agility.
potato