noun
Etymology: so called from the allegation of Commodore Stephen Decatur died 1820 American naval officer that on the night of December 12, 1813 American Federalists traitorously signaled to the British by means of blue lights on either end of the mouth of the harbor at New London, Conn.
: a member of that wing of the American Federalist party that bitterly opposed the War of 1812 — usually used disparagingly