noun: (philately) Initialism of first day cover. [(philately) A letter or card with new stamp, posted on the day that the stamp was first issued.]
noun: (US) Initialism of federal detention center.
noun: (anatomy) Initialism of follicular dendritic cell. [(anatomy) A specific type of cell, found in lymphoid follicles having filiform dendrites that bind and present immune complexes to B cells.]
adverb: (dance) Initialism of facing diagonally to the center.