An all-time low, or ATL, is the opposite of an ATH - it's the lowest price a coin or token has ever reached. It's like the crypto equivalent of hitting rock bottom.
When a coin hits an ATL, the mood in the crypto community is pretty grim. You'll see a lot of people posting about their losses, cursing the day they ever heard of crypto, and vowing to never invest again (until the next bull run, of course).
Example
"I can't believe I bought this coin at its ATH, and now it's hit a new ATL. I feel like such a fool."
"Some people are saying this ATL is a good buying opportunity, but I'm not so sure. What if it keeps going down?"
"I told my friend to buy this coin when it was at its ATL, but he didn't listen. Now it's up 500%, and he's kicking himself."
