The Collaborative International Dictionary of English v.0.48:
Peanut butter \Pea"nut but"ter\ A paste made by mixing ground fresh roasted peanuts with a small quantity of water or oil, and used chiefly as a relish on sandwiches, etc. [Webster 1913 Suppl.]WordNet (r) 3.0 (2006):
peanut butter n 1: a spread made from ground peanuts