̷ ̷ˌ ̷ ̷ ̷ ̷ˈrāshən noun
( -s )
Etymology: Latin acceleration-, acceleratio, from acceleratus + -ion-, -io -ion
1. : the act or process of accelerating
the unusual acceleration of economic activity
: state of being accelerated
2. : the time rate of change of velocity (as in speed or direction) : the vector derivative of the velocity with respect to time — see angular acceleration
3. : gradual appearance in the course of evolution of an ancestral adult character in the immature descendant — compare abbreviation
4. : advancement in mental growth or achievement beyond the average of one's age