As in, technically you are 'volunteering' to help lead a committee, take on a new role at work or maybe raise your hand in a meeting to offer help.
But really, you are more or less being 'forced' due to manager insistence, nagging from others, or generally giving in to peer pressure.
"My boss really wanted someone she trusted to head up the new project and since I'm that good, she more or less volunforced me by singing my praises in a meeting and getting everyone else on board to back her up. Secretly though, I'm really not interested in taking that project on, but who am I to resist?"
When a co-worker contacts you about a descrepancy that isn't really there if they knew how to read the data you've schooled them on three times already or a frequent mistake that you've tried to correct repeatedly and it's just not sinking in.
"Another descrapancy email from Kyle in Accounting rejecting my expense report due to lack of receipts, when I've sent copies to him twice already."