The correct spelling is "subtle" but you do not pronounce the " b" so it sounds like "sutle". It means delicate, thin, hard to perceive, see or understand. The song is about an intimate relationship. The subtle things between people in a relationship are small, seemingly insignificant things that in truth are very important and can have deep emotional impact.

Esto significa "las cosas triviales".

Fun.'s "We Are Young": "between the drinks and subtle things" "subtle" = Spanish "sutil" (In English, the letter "b" is silent in the word "subtle.")

Basically it's an expression that is used when one has done something without drawing much attention to themselves. But in your case your friends being sarcastic so he said 'suttle' because the vibiration gave you cellphone away> therefore the sarcasm insert. http://answers.yahoo.com/question/index?qid=20080903162440AA1fZFD