Complex sentence: A metacompiler is a computer program that reads as input a metalanguage program in which a programming language specification of the syntax of a programming language plus a its semantic equivalent transformation to object code, i.e. of its equivalent in terms of a target language.
Split into simpler sentences: A metacompiler is a computer program that reads as input a metalanguage program. A specialized programming language in which a programming language specification of the syntax of a programming language plus a its semantic equivalent transformation to object code, i.e. of its equivalent in terms of a target language.