The Collaborative International Dictionary of English v.0.48:
Fanion \Fan"ion\, n. [See Fanon.] 1. (Mil.) A small flag sometimes carried at the head of the baggage of a brigade. [Obs.] [1913 Webster] 2. A small flag for marking the stations in surveying. [1913 Webster]WordNet (r) 3.0 (2006):
fanion n 1: a small flag used by surveyors or soldiers to mark a position