A class of language grammars, which can be parsed without backtracking. The first L stands for Left-to-right scan, the second for Leftmost derivation.
Often found in the form LL(k) where k is the number of tokens of look-ahead required when parsing a sentence of the language. In particular, LL(1) is a fairly restrictive class of grammar, but allows simple top-down parsing (e.g. recursive-descent) to be used without wasteful backtracking. A number of programming languages are LL(1) (or close).