Hey Madhav.

MHCET LAW is an entrance test for admission in Law course on various law colleges of Maharashtra. There are 85% seats reserved for the candidates who have a domicile of Maharashtra. Rest of the seats belong to the candidates from rest of the states. Hence OMS means Outside Maharashtra state. So the ranking of all the candidates from outside of Maharashtra is considered for the left seats which is the OMS Ranking.

Best of luck