fall in

fall in idiom
  1. Take one's place in formation or in the ranks, as in The sergeant ordered the troops to fall in. A related expression is fall into, as in They all fell into their places. [Early 1600s] Also see fall into.
  2. Sink inward, cave in, as in The snow was so heavy that we feared the roof would fall in. [Early 1700s] Also see under drop in; the subsequent idioms beginning with fall in; fall into.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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