Meaning of “plug” - Learner’s Dictionary

plug

verb [ T ] uk us /plʌɡ/ (present participle plugging, past tense and past participle plugged)
plug a gap/hole mainly UK

to solve a problem by supplying something that is needed:

The new computer system will help to plug the gap in the county's ability to collect taxes.
ADVERTISE

to talk about a new book, film, etc in public in order to advertise it:

He was on TV, plugging his new book.
HOLE

to block a hole

(Definition of “plug verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)