1. To remain inside (of something or some place). Officials are warning people to keep inside during the storm. Everyone keeps inside their homes with the air conditioning cranked up during these heatwaves.
2. To cause someone or something to remain (in something or some place). In this usage, a noun or pronoun is used between "keep" and "inside." You can't keep kids inside for that long, or they start getting really bad cabin fever. Please keep the dogs inside the house while I mow the lawn.
3. To store something or house someone inside of something or some place. In this usage, a noun or pronoun is used between "keep" and "inside." You really shouldn't keep classified documents inside your desk drawer like that. Anyone could come along and take them! Officials kept the refugees inside the football stadium, which had been repurposed as an emergency shelter.
4. To be unable or unwilling to express or share some emotion or information. In this usage, a noun or pronoun is used between "keep" and "inside." It was really hard keeping such a big secret inside for so long, but I can finally share the news with everyone! It isn't healthy to keep your anger inside like that.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
keep something inside
((of) one(self)) Go to hold something in.
keep inside (of something)
to remain inside of something, usually a shelter, house, etc. (Of is usually retained before pronouns.) Please keep inside of the house while it's raining. I want you to keep inside.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.