Webster's Collaborative New Word Dictionary - F
farbrengen (n.): a Hasidic gathering, usually with eating, drinking, singing, and discussion of hasidic teachings, held especially on the Sabbath and other festivals.
farkakte (adj.): covered in excrement. Rare.
flag-off (n.): the moment at which a race, esp. a motor race, is flagged off; the start of a race. Now chiefly Indian English.
fletched (adj.): of an arrow: fitted with feathers or vanes. Frequently with a modifier, as feather fletched, high fletched, etc.
Foucauldian (adj. and n.): of, relating to, or characteristic of the ideas or works of the French philosopher and historian Michel Foucault.
franger (n.): a condom.
futzing (n.): ineffectual or trifling activity; messing about; tinkering. Chiefly with around.