Note: lately, the word has been abused in popular culture to label something popular that the speaker simply dislikes or has an objection to on principle. Among fans of hip-hop, said speaker is often deemed a hater. In extreme cases, he/she is labeled a punk bitch.
Also note, there is no such thing as "overrated" in indie culture. When the word is uttered in the presence of an indie kid, it is often followed by disembodied moans and howls and said person melting like a snowball in Hell.
Person 2: Amen to that.
Person 1: Lana del Rey is so overrated.
Person 2: U jelly?
Person 1: Jay-Z is so overrated.
Hip-hop fan: You betta shut the fuck up, jealous punk bitch hater!
Person 1: Dude, Radiohead is so overrated.
Indie kid: AHHHHHOOOOOOOOHBLAAAAAAH! I'm MEEEEELLLLTIIIING!
All good examples of this word. It means something that is popularized but really isn't all that great. i.e. my chemical romance.
Your mother is overrated.