Lewis & Short

stŏmăchōsus, a, um, adj. [stomachus, II.], wrathful, angry, irritable, ill-humored, peevish, pettish, choleric (rare but class.; syn. iracundus): eques, Hor. Ep. 1, 15, 12: stomachosa et quasi submorosa ridicula, Cic. de Or. 2, 69, 279: genus acuminis saepe stomachosum, id. Brut. 67, 236: genus irarum, Sen. Ira, 1, 4, 2.
Comp.: stomachosiores litteras meas, quas dicas esse, non intellego, Cic. Fam. 3, 11, 5.
* Adv.: stŏmăchōsē, angrily, peevishly; comp.: rescripsi ei stomachosius, Cic. Att. 10, 5, 3 (cf. id. ib. 10, 11, 5: θυμικώτερον eram jocatus, id. ap. Charis. 193 P.).