volunteer

ilmoittautua vapaaehtoiseksi, tarjota, tarjoutua vapaaehtoiseksi

vapaaehtoinen

kertoa vapaaehtoisesti One who enters into, or offers for, any service of his/her own free will, especially when done without pay.
puhekieltä One who enters into military service voluntarily, but who, when in service, is subject to discipline and regulations like other soldiers; -- opposed to conscript; specifically, a voluntary member of the organized militia of a country as distinguished from the standing army.
puhekieltä A person who acts out of his own will without a legal obligation, such as a donor.
puhekieltä A plant that grows spontaneously, without being cultivated on purpose; see (w) in Wikipedia.
A native or resident of the American state of Tennessee.
puhekieltä To enlist oneself as a volunteer.
puhekieltä To do or offer to do something voluntarily.

to volunteer for doing the dishes

to volunteer an explanation

My sister volunteered me to do the dishes.