Answer: giddyap

AnswerCrossword Clue
GIDDYAP"Hi-yo, Silver!"
GIDDYAPRider's command
GIDDYAPOpposite of whoa
GIDDYAP"Move it!"
giddyap(used as a command to a horse to speed up)
giddyapused to tell a horse to go faster, also GIDDAP, GIDDYUP