noun, used as a suffix
Abbreviation of トレーニング, used as a suffix in compounds like 筋トレ (muscle training) or イメトレ (image training). Not used as a standalone noun.
毎朝、筋トレをしている。
I do muscle training every morning.
試合前にイメトレを欠かさない。
I never skip image training before a match.