Definitions for "Tevul yom"
(immersed on that day) a person who has incurred one of the uncleannesses for which Scripture ordains "he shall be unclean until evening," has immersed him or herself in a mikveh, and now awaits the day's end to be ritually pure (see Mishnah Kelim 1:8).
a person or utensil that has been immersed in a Mikvah to become Tahor for Chulin, but is still waiting for nightfall to be completely Tahor with regard to Terumah
a person or vessel that has immersed in a Mikvah, but requires night to fall before becoming completely Tahor