tip of my tongue 

a phrase used to describe a word you can not think of because you don't know it. You use this phrase when you have no knowledge of the proper word to imply that you have simply forgotten. With use of this phrase, you appear no less intelligent, merely forgetful.

1. "Hey Marvin, whats the name of that actor... the one from Forrest Gump?"

"Aw damn, I totally know who you are talking about, the name is on the tip of my tongue..."

"Its okay, we all forget sometimes."

2. While playing charades:

"Oh no! I can tell what you are doing! it is on the tip of my tongue!!"

"TIMES UP! It was jitter-bug."

"See! I knew that, i just couldn't think of the word."

tip of my tongue by whattheface May 1, 2011

it's at the tip of my tongue 

When a person cannot remember something.

I cannot remember what day I have to go to the office, it's at the tip of my tongue!

it's at the tip of my tongue by Madinerrr July 5, 2006

On the tip of my tongue 

knowing something that cannot immediately be recalled, like a well-known word or familiar name. When experiencing it, people feel that the blocked word is on the verge of being recovered. Despite failure in finding the word, people have the feeling that the blocked word is figuratively "on the tip of the tongue."

I can't remember the word for eating pussy, but it's right on the tip of my tongue.
I can't remember the word for licking balls, but it's right on the tip of my tongue.
I can't remember the slang word for "anus," but it's at the tip of my tongue.

On the tip of my tongue by derbyjames January 1, 2010