The phrase "arrival en masse" is often used to describe a large group of people or things arriving at the same time. However, there are many other words and phrases that can be used instead of this expression. For example, "in droves," "en masse," "in large numbers," "all at once," "simultaneously," "in huge crowds," "in an overwhelming swarm" and "in a deluge." These synonyms are effective in conveying the idea of a multitude of individuals or items arriving simultaneously. By using these alternative phrases, writers can add variety to their language and avoid repetition of the same phrases.