Found:

bounding node

SYNTAX: node that plays a role in determining whether a movement is local enough; see Bounding theory. Traditionally, NP and S (in English) or S' (in Italian) are considered bounding nodes. More recently, bounding nodes have been defined in terms of barriers.

LIT.	Chomsky, N. (1986b) Chomsky, N. (1981) Rizzi, L. (1982)