When you have a strong feeling that you have heard a familiar song before and you associate it with a time or an emotion, but you aren't exactly sure when or where you have heard the song. This usually occurs most strongly at the beginning of the song, but can last the entire duration as well.

Noun: a friend who is usually only called upon by a friend when a more primary/prominent friend is unavailable.

Taken from the term “second string” in an athletic competition situation. In football, if the star quarterback gets injured during a play, the second string is called off the bench to replace him/her. A “Second String Friend” is essentially benched until needed, if ever.

Synonyms: Plan B, Second Choice, Secondary Friend, Benched Until Needed

when you are listening to your ipod or mp3 player to a song and you realize the same song is playing in the background at the same time (or very close to)