a spontaneous gift (Ex 35:29), a voluntary sacrifice (Le 22:23; Ezr 3:5), as opposed to one in consequence of a vow, or in expiation of some offence.
And the children of Israel brought willing offerings unto the LORD; both men and women, as many as their hearts made them willing to bring, for all manner works which the LORD had commanded to make by the hand of Moses.
An ox or a sheep that hath any member out of proportion, mayst thou offer for a freewill offering: but in a vow it shall not be accepted.
Afterward, the daily burnt offering also, and of the new moons and of all the feast days of the LORD that were hallowed, and all manner of freewill offerings, which they did of their own freewill unto the LORD.