The definition of intertwine is to join things by combining together.(verb)
When you start to share a house with someone and your possessions get mixed together and you begin to share each other's friends and activities, this is an example of a time when your lives begin to intertwine.
See intertwine in Webster's New World College Dictionary
See intertwine in American Heritage Dictionary 4
tr. & intr.v. in·ter·twined, in·ter·twin·ing, in·ter·twines
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