Lewis & Short

fissūra, ae, f. [findo]; a cleft, chink, fissure (post-Aug.): quorum in digitos pedum fissura divisa est, Plin. 10, 63, 83, § 176: vitis, Col. 4, 29, 4.
In plur., Plin. 33, 6, 33, § 101: efficax asini sevum labrorum fissuris, chapped lips, id. 28, 12, 50, § 188.