A conventional use of the 2NT when partner's 1NT opening has been overcalled. There are numerous examples of Lebensohl being used in other situations - refer to section 1 of the 'Conventions [..]

(usually lower case initial letter, superseding all other capitalization rules, to imply its having been erroneously named) a two-notrump bid asking partner to bid three clubs, after which a suit bid [..]