A syntagma s.l. is discontinous iff not all of its parts are adjacent. Discontinuity of a linguistic unit is its property of being discontinuous.

In a sequence A X B, A ...B is discontinuous only if the construction cannot be analyzed as [AX]B or A[XB], i.e. only if A...B behaves as a whole with regard to X or to other parts of the context.

Examples: the French negative ne...pas.
The compound verb in Linda put Paul off.
The finite verb form in German Paul hat das Buch gelesen. "Paul has read the book."