Definitions of lock in period
the time period during which a borrower may not start repaying a loan without paying penalties
Make sure you have time to send in your cancellation form to your current bank and avoid prepayment penalties should you refinance before the lock-in period is over.
the time period for which a lender has agreed with the borrower to hold a certain interest rate unchanged
Lenders that charge rate lock fees generally charge higher fees for longer lock-in periods.