1 fóst-bróðir
m. a foster-brother:
2 fóst-bróðir
1. prop. of men brought up together, brothers in arms, and the like; Arinbjörn hersir var f. Eireks konungs, Eg. 401, Fs. 121, 139, Fms. x. 226, Ísl. ii. 219; frændr ok fóstbræðr, Fs. 120, 122; þeir vóru vænligir menn ok görðusk fóstbræðr (brothers in arms) Ingimundar, 13, 15, 16, 19, 24, passim.
3 fóst-bróðir
2. a sworn brother, = eiðbróðir, pledged by the rite of blending blood together (vide bróðir), Gísl., Fbr., passim: hence Fóstbræðra-saga, u, f. the name of the history (but the name is mod.); fóstbræðra-lag, n. a foster-brotherhood, Eg. 116. 165, Fms. vii. 25, passim:—sworn brotherhood, sverjask í f., Fms. iii. 213, cp. esp. Gísl., Fbr.