I think in the most common sense, the blade config (clip and
full-length spey) are what define the trapper. There was a thread recently (linked below), featuring an older 6207 pattern from Case, which (in the case of the knife posted by the OP) was a 'serpentine jack' with clip and pen blade, in a trapper-like handle pattern that Case had later also made into a medium/small 'mini-trapper' config (same frame, but featuring the clip and long spey blade).
http://www.bladeforums.com/forums/showthread.php/1002529-Question-about-Case-6207
Case has also made a 'Moose' pattern (6275), which is usually a large-framed folder with clip and long spey, but each blade pivoting from opposite ends of the handle. I have seen it also referred to as a trapper pattern, no doubt based on the inclusion of the long spey.
David