bipennis means an axe with an edge or blade on each side of the handle. Lexicurio rates it Sui generis — a strength score of 87 out of 100.
noun
- An axe with an edge or blade on each side of the handle.“Bipennis... A twibill, axe, or twall, sharpe on both sides, wherewith carpenters make mortaises: it was in old time a weapon”