Increases rapidly (7)
I believe the answer is:
rockets
(Other definitions for rockets that I've seen before include "Spaceships" , "moves fast" , "Their science is notoriously hard" , "Shoots up abruptly" , "Self-propelled missiles" .)
I believe the answer is:
rockets
(Other definitions for rockets that I've seen before include "Spaceships" , "moves fast" , "Their science is notoriously hard" , "Shoots up abruptly" , "Self-propelled missiles" .)