1. Wally from "Where's Wally?" (or "Where's Waldo?"): This is the most common meaning. "Waldo" is the name of the character in the popular children's book series and game "Where's Wally?" (or "Where's Waldo?"). The books feature a red-and-white-striped man named Wally (or Waldo) hidden within busy, detailed illustrations, and the challenge is to find him.
2. A person named "Waldo": It's also a legitimate, though uncommon, first name.
3. Slang term for "wallet": In some regions, "Waldo" is a slang term for a wallet.
4. A type of ice cream: "Waldo" is also a brand of ice cream in some areas.
To understand which "Waldo" you're looking for, more context is needed. What was the situation where you heard the word "Waldo"?