What does “420” mean?
When California teens in the 1970s needed a covert way of discussing their after-school plans, they used their meeting place and time as shorthand to avoid suspicion. Eventually, they shortened the phrase to just the time they would often meet after track practice, 4:20 pm. Soon after that, they used the number 420 as code for getting high. To this day, 420 has a major place in cannabis culture, and while it's not much of a code word anymore, it's a quick way to get your point across. April 20th is now an unofficial holiday for most users, and chances are if you're smoking with a group of buddies around 4:20 pm, one of them will point out the clock when it rolls around.
Example usage for 420
“I'm looking for a 420-friendly roommate to fill my empty room because I don't want a roommate who doesn't smoke weed.”