(Entry lacking, Adler reports, in mss FV and a marginal addition in A.)
No equivalent entry in other lexica. The glossing phrase, nevertheless, is standard terminology in grammars (esp. Apollonius Dyscolus and Herodian), scholia and elsewhere for asserting that a locution sometimes found as two words -- in this instance the prepositional phrase e)f' o(/son -- is better written as one.
cf. under alpha 1(a), eta 292, pi 2102