prolific

(adjective) very productive
Noam Chomsky is a very prolific author. He's written many books and articles.


tangible


(adjective) touchable, perceptible by touch
Max will probably escape punishment for his crimes because there is no tangible evidence to make a case against him.


ad lib

 (verb) to speak or perform without preparing previously, improvise
The teacher lost all of his teaching notes on the way to class and was forced to ad lib the lesson