Auto-Exercise
The broker or clearing process of automatically exercising eligible ITM options at expiration.
Explanation
Most U.S. equity options that are at least $0.01 in the money at expiration are automatically exercised unless you submit contrary instructions. Auto-exercise can create unexpected stock positions and weekend gap risk if not managed before close.
Example
A 150 call expires with stock at 150.08; the contract is auto-exercised and becomes long 100 shares.