This is how you sign Impractical in American Sign Language.

To sign "Impractical" in American Sign Language (ASL), follow these steps:                                        

1. Form your dominant hand into an "A" hand with the thumb extending a bit more than normal. Place the thumb under your chin. Quickly move your hand forward a few inches.                                                                                                                                      2. Generally you use a negative headshake with this sign.