sign in

sign in idiom
Record one's arrival by signing a register, as in He signed in both himself and his wife. [c. 1930] For the antonym, see sign out.

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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