Alternately
Surely making a gerund of the verb turns it into a noun.
( flake has nothing against your right leg, Mon 23 Feb 2009, 23:12, 1 reply)

then shouldn't it be
Heather and Bill saddlebackinged all night

?
( djtrialprice, Mon 23 Feb 2009, 23:35, closed)

Grammar 101
No, saddleback is the verb. Saddlebacking is the gerund, and therefore a noun. The definition given - "the phenomenon of..." - matches the word, because phenomenon is similarly a noun, but the indicator of the word type - "vb" - does not.

In other words, the OP should look like this:
Saddlebacking: sad•dle•back•ing \ˈsa-dəl-ˈba-kiŋ\ noun [fr. Saddleback Church] (2009): the phenomenon of Christian teens engaging in unprotected anal sex in order to preserve their virginities.

If the definition was for saddleback then it would look something like this:
Saddleback: sad•dle•back \ˈsa-dəl-ˈbak\ vi [fr. Saddleback Church] (2009): to engage in unprotected anal sex in order to preserve one's virginity.
( flake has nothing against your right leg, Tue 24 Feb 2009, 19:29, closed)