While the contract language may seem ambiguous, unfortunately, the terms and definitions within come straight from the FARs:
FAR 121.433
(1) Crewmembers who have qualified and served as a crewmember on another type airplane of the same group may serve in the same crewmember capacity upon completion of transition training as provided in §121.415.
(2) Crewmembers who have qualified and served as second in command or flight engineer on a particular type airplane may serve as pilot in command or second in command, respectively, upon completion of upgrade training for that airplane as provided in §121.415.
For your benefit, I've included a snippet about what a "group" is (as referenced in part 1 in the previous quote):
FAR 121.424
(1) Group I airplanes—
(i) Reciprocating powered. Pilot in command, 10 hours; second in command, 6 hours; and
(ii) Turbopropeller powered. Pilot in command, 15 hours; second in command, 7 hours.
(2) Group II airplanes. Pilot in command, 20 hours; second in command, 10 hours.
Like I said, there's unfortunately not a whole lot of gray area in terms of what counts as "transition" and "upgrade". Because turboprop (I.E. EMB120) is not in the same training "group" as a turbojet (I.E. CRJ), you must use the "upgrade" phraseology instead of the more lenient "transition" phraseology.