[Fe.ni.an] n [Ir feinne, pl. of fiann, legendary band of Irish warriors] (1816) 1: a member of a legendary band of warriors defending Ireland in the 2d and 3d centuries a.d.
2: a member of a secret 19th century Irish and Irish-American organization dedicated to the overthrow of British rule in Ireland -- Fenian adj -- Fe.ni.an.ism n