It describes an action or decision done with hesitation or against one's will, often due to a feeling of obligation or pressure.
Here are some synonyms for reluctantly:
* unwillingly
* hesitantly
* grudgingly
* unwillingly
* with misgivings
* with reservations
* against one's will
* halfheartedly
Example:
"She reluctantly agreed to go to the party, even though she didn't feel like it."