This is the 787th most frequent French word.
rapide
Quick; fast.
Here, 'rapide' is used as an adjective to describe the speed characteristic of the horse in its activity.
Le cheval est très rapide en course.
The horse is very fast in the race.
In this context, 'rapide' transforms into 'rapidement' to function as an adverb, indicating the manner in which the action (responding) should occur.
Réponds-moi rapidement avant demain.
Respond to me quickly before tomorrow.
Here, 'rapide' is used as an adjective to qualify the noun 'solution', describing the characteristic of being quick or efficient in resolving issues.