it was used in the episode Hungry Hungry Homer originally aired on March 04 2001.
Bart + Lisa: Meh.
Homer: But the TV gave me the impression that --
Bart: We said, "Meh!"
Lisa: M-e-h, meh.
2. A sound made when the speaker does not care at all and just wishes the other person woulod get the hell off that specific topic.
3. A verbal shrug.
4. The most useless and pointlessly futile word that gets people nowhere, does nothing, explains not much whatsover and, to top it all off, is effortlessly annoying for the rest of the participants in the conversation.