A good omen, as distinguished from tiyarah, “a bad omen”.
Muhammad is related to have said, “Do not put faith in a bad omen, but rather take a good one.” The people asked, “What is a good omen?” And he replied, “Any good word which any of you may hear.”
Ibn Abbas says, “The Prophet used to take good omens by men’s names, but he would not take bad omens.”
Qat’an ibn Qabisah says, “The Prophet forbade taking omens from the running of animals, the flight of birds, and from throwing pebbles, which were done by the idolators of Arabia.” (Mishkat, book xxi c ii)
It is, however, very commonly practised amongst the Muslims of India. For example, if a person start out on an important journey and he meet a woman first, he will take it as a bad omen, and it he meet a man he will regard it as a good one.
Based on Hughes, Dictionary of Islam