A dense word is a word that crowds a lot of meaning into a small space. The fewer words you use to express an idea, the more impact that idea will have. When you revise, look for opportunities to cross out several words and insert one. Once a month is monthly; something new is novel; people they didn’t know are strangers; and something impossible to imagine is inconceivable.
Taken from “100 Ways To Improve Your Writing” by Gary Provost ISBN 978-0-451-62721-6