army volunteer
To select, nominate, or assign someone to carry out a task or duty that they are unwilling or unprepared to undertake. My boss always army volunteers me to pick up lunch for the office.
volunteer as something
to submit oneself as a person ready or willing to do something. Would you be willing to volunteer as a marcher? I will volunteer as a helper in the hospital.
volunteer for something
1. to submit oneself for some task without being asked. Ivolunteered for the job. I didn't volunteer for this.
2. to work as an unpaid volunteer for a charity, etc. On Sundays she volunteers as a receptionist at the hospital.