The<unk>  <unk>  phenomenon is an instance of knowing something that cannot immediately be recalled. <unk>  is a near-universal experience with memory recollection involving difficulty retrieving a well-known word or familiar name.  When experiencing<unk> , 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<unk> ."  Inaccessibility and the sense of imminence are two key features of an operational definition of<unk> s (A.S. Brown, 1991).
Tip of the tongue
Hard palate
Veratrum
Nail 
Cauliflower ear
Ramus of the mandible
Palatine tonsil
Pterygium