A battle axe (also battle-axe or battle-ax) is an axe specifically designed for combat.
Battle axes are specialized versions of utility axes. Many are suitable for use in one hand, while others are larger and used two-handed. Axes designed for warfare range in weight from just over 0.5 kg to 3 kg (1 to 6 pounds), and in length from just over 30 cm to upwards of 1.5 m (1 to 5 feet). Cleaving weapons longer than 1.5 m would arguably fall into the category of polearms.
Pathfinder RPG Core Rulebook. Copyright 2009, Paizo Publishing, LLC; Author: Jason Bulmahn, based on material by Jonathan Tweet, Monte Cook, and Skip Williams.