If you go by the meaning of Veto, it refers to have a constitutional right to reject a decision or proposal made by a lawmaking body. It's the supreme power of a member who got the edge over others to block any proposal or resolution single-handedly in an organization.
In terms of talking about United Nations Security Council, Veto power refers to the power of permanent members (UK, USA, France, China and Russia) to pass or oppose a strong resolution single-handedly. However, absence of a permanent member doesn't prevent a draft resolution from being adopted.
United Nations Security Council has five permanent members at present and ten are temporary that get term on a rotational basis. The permanent members have this power because of being nuclear powers and they can block any resolution in the council.
India does not have Veto power even Iranian President, Hassan Rouhani on Friday questioned the same why India with a population of over 1 billion does not have Veto power at the UN Security Council (UNSC) while the US does. He further added that having veto rights only to the five nuclear powers at the time of the UNSC's formation was unfair.