Sub·cal'i·ber adjective Smaller than the caliber of a firearm. [ Written also subcalibre .] Subcaliber projectile , a projectile having a smaller diameter than the caliber of the arm from which it is fired, and to which it is fitted by means of a sabot. Knight. Found on http://www.encyclo.co.uk/webster/S/220
• (a.) Smaller than the caliber of a firearm.
Sub·cal'i·ber adjective Smaller than the caliber of a firearm. [ Written also subcalibre .] Subcaliber projectile ,