U+2195 · emoji since 2010
The up-down arrow points both ways vertically. It means moving up and down, resizing, and scrolling either direction.
It marks toggling height and going both ways, the simple sign for up or down.
In texting, ↕️ does not carry a widely used hidden or slang meaning, so you can usually take it at face value. People send it just as it looks, to add a little visual touch or set the mood of a message. Only a handful of emoji have a separate texting code, and ↕️ is not really one of them.
Its official Unicode name is the Up-Down Arrow emoji. In everyday chat most people just call it the up-down arrow emoji or describe what it shows. Copy and paste it from the button at the top of this page.
The ↕️ leads off a short phrase, and the rest of the words are written in cipher, every letter disguised as another emoji. Tap decipher to reveal the whole line.
Or make your own cipher in the translator.