tl;dr, short for "too long; didn't read", is 📝Reddit slang to say that some text being replied to has been ignored because of its length. In slang it can also stand for "Too lazy; didn't read". It is also used as a signifier for a summary of an online post or news article.

Contexts

• 🏷️#reddit-lexicon (See: 📝Reddit Glossary)
• 🏷️#index (See: 🏷️#index)