from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A sterile or otherwise sexually imperfect female calf born as the twin of a bull calf.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A female calf, born as twin with a bull calf, but sexually imperfect (often infertile).
Perhaps akin to Irish Gaelic mart, heifer.(American Heritage® Dictionary of the English Language, Fourth Edition)
Etymology unknown. (Wiktionary)