run up on

From run up +‎ on.

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run up on (third-person singular simple present runs up on, present participle running up on, simple past ran up on, past participle run up on)

1. (transitive) To approach with speed or forceful intensity

   Hey, don't run up on me like that while my back's turned...I might accidentally deck you.

2. (transitive, African-American Vernacular) To confront with hostility
3. (transitive, African-American Vernacular) To hit on (somebody).