Employers often make up their own abbreviations for amounts they put in box 14. Ask them---that would be better than having us guess.
Box-14 of your W-2 is used by your employer to report amounts that don't go in any other boxes of your W-2. You will need to check with your employer to find out what TRANS is. Do you get any type of commuter transportation benefits? It may be that.
Refer to the TurboTax article What is box 14 on my W-2 for?
@Anonymous
Thank you - yes, I get transportation benefits that are tax deductible, and yes, it seems to be. Does it mean this amount is excluded from my taxable income?
Box 14 is an information box. Nothing in box 14 affects your federal return, and employers can put anything there that they want. (Some states may use box 14 for items that affect your state taxes, and turbotax knows about most of these things.)
You need to ask your employer for a definite answer. It is not a new or separate tax deduction (it can't be under law) so my guess is that it is a notation or reminder of something that was already excluded from your box 1 taxable wages.