On the tip of your tongue
Definition 1 of 1
Pro Tip 1/3Memory Lapse
Use when you almost remember something; it suggests a brief struggle to recall. 
I know the capital of France, it's just on the tip of my tongue!
Pro Tip 2/3Spoken Context
Commonly used in conversation rather than written form; indicates a casual tone. 
You know that movie we watched? The director's name is on the tip of my tongue.
Pro Tip 3/3Frustration Expression
Indicates a sense of mild annoyance or frustration at being unable to recall. 
Ugh, the word I want to use is on the tip of my tongue!