taking the morning off; morning leave
Used in workplace or school contexts when someone takes leave only for the morning, often with the intention of coming in later. Common in business Japanese.
I'm taking the morning off today and will come to the office in the afternoon.
I wasn't feeling well, so I took the morning off.
半休 is a general term for half-day leave, which can be either morning or afternoon. 午前休 specifies the morning half.
Compound of 午前 (gozen, 'morning') and 休 (kyū, 'rest' or 'leave'). A straightforward modern formation.