Wiktionary
quasigroup
n. (context mathematics English) An algebraic structure, resembling a group, whose arithmetic may not be associative
Wikipedia
Quasigroup
In mathematics, especially in abstract algebra, a quasigroup is an algebraic structure resembling a group in the sense that " division" is always possible. Quasigroups differ from groups mainly in that they need not be associative.
A quasigroup with an identity element is called a loop.