Gossip, blab, tattle mean to disclose something that one would have done better to keep to oneself.
To gossip is to communicate or exchange in conversation remarks, often uncomplimentary or damaging and of questionable veracity, about the private affairs of others, especially acquaintances or neighbors.
To blab is to disclose something private or secret that has been confided to one or that has come to one’s knowledge.
Tattle sometimes is more closely akin to gossip, sometimes to blab, or it may combine the implications of the two. It suggests loose and loquacious gossip, or unsolicited revelation to one having power of discipline or punishment of some trivial misdeed on the part of another, or blabbing gossip that is usually a betrayal of confidence.