DEF#1-(n): A code word for warning.
DEF#2-(v. intr.): A word of warning indicating one to cease an action that was occuring, or was about to occur.
EX#1: If you and a friend are talking about someone or something in secret and an involved party approaches, the one who sees the individual would say, "YARNIT", indicating to the other to stop whatever it is they were saying or were about to say for fear that the indivual might hear it.
EX#2: When two or more people are involved in any form of cheating or stealing, one would say to the other,"YARNIT", if an authority figure, (teacher, policeman, retail employee etc.), was approaching.