In addition to the definitions previously mentioned, "fair enough" can also be used to mean "fine; have it your way" (if you are trying to persuade somebody or show them a better way to get something done and they won't listen).
On a slightly unrelated note, I've found that a lot of native speakers make this mistake: It's "all right", not "allright" and definitely not "alright". Same goes for "never mind" and "a lot" - all of them are made up of two words.