at the tip of one's tongue

at the tip of one's tongue or on the tip of one's tongue  {adv. phr.}

 {informal}

1. Almost spoken; at the point of being said.

It was at the tip of my tongue to tell him, when the phone rang.

John had a rude answer on the tip of his tongue, but he remembered his manners just in time.

2. Almost remembered; at the point where one can almost say it but cannot because it is forgotten.