Lewis & Short

excūsābĭlis (excuss-), e, adj. [excuso], that may be excused, excusable (very rare; not in Cic.): delicti pars, Ov. P. 1, 7, 41.
Comp.: error, Val. Max. 8, 11, 4.
Adv.: excūsābĭlĭter, excusably, Alcim. Avit. Homil. Fragm. 2.
Comp.: excusabilius peccat, Aug. Trin. 17, 15 fin.