Definition of "metatheoretical"

OK – I can hear you objecting – I can see how this 'no crossing branches' constraint can be made to work mechanically, but what on earth is the point of it? Why should it matter whether branches can or cannot cross? A good question (if you asked it for the right reasons, and not just because you're be- ginning to get exasperated with Syntax!) Well, the motivation behind this con- straint is essentially as follows: on general metatheoretical grounds (the desire to develop a maximally constrained theory which provides a plausible basis for developing a model of language acquisition), we want to restrict the class of P-markers which qualify as 'possible natural language sentence-structures' as narrowly as possible, and rule out as many 'impossible' structures as we can.

1988, Andrew Radford, Transformational grammar: a first course, Cambridge, UK: Cambridge University Press, page 122

In conclusion I will evaluate the gains achieved by formalising ITT from a metatheoretical point of view.

2008, Frieder Lempp, “The Logical Structure of International Trade Theory”, in Erkenntnis, volume 69, number 2