What is "shm-reduplication"

Shm-reduplication is a form of reduplication in which the original word or its first syllable (the base) is repeated with the copy (the reduplicant) beginning with shm- (sometimes schm-), pronounced . The construction is generally used to indicate irony, derision, skepticism, or disinterest with respect to comments about the discussed object:

He's just a baby! "Baby-shmaby". He's already 5 years old! What a sale! "Sale, schmale". I'm waiting for a larger discount.

The original word can be a noun, but also an adjective:

"Whenever we go to a fancy-schmancy restaurant, we feel like James Bond."

In general, the new combination is used as an interjection. In the case of adjectives, the reduplicated combination can belong to the same syntactical category as the original.