it is a secret symbol...if you turn you're head 90 degrees to the right it looks like a man sititng on his porch smoking some weed

Noun connoting any fraud, confidence trick, form of cheating or dishonesty.

This denotes any act which relates to, falls under, or is described by, Indian Penal Code Section 420. This section reads as follows: "420. Cheating & dishonestly inducing delivery of property.-- Whoever cheats & thereby dishonestly induces the person deceived to deliver any property to any person, or to make, alter or destroy the whole or any part of a valuable security, or anything which is signed or sealed, & which is capable of being converted into a valuable security, shall be punished with imprisonment of either description for a term which may extend to seven years, & shall also be liable to fine." - IPC, Section 420. ( indiankanoon.org/doc/1436241, vakilno1.com/bareacts/IndianPenalCode/S420.htm)

420 means national weed smoking day, also it is a number between 419 421.

420 is the stoner’s holiday.
420 refers to April 20th, at 4:20, when stoners world wide blaze.

That date of 420 originated because 420 is the code cop’s use when they sited a large drug operation.

A day almost like 420 where people must smoke as much reefer as they can. It marks the ending point of a month long bet, between friends who did not smoke for that whole month, and on that end date the calendar read 1027 (october, 27th).

An acquaintance who makes it possible for 420 to take place. Either being a 'middle-man' in the hook-up or building the actual spliff themselves.

Yes, it's true that the "Waldos" were some of the first people to coin the phrase 420, but, before the "Waldos" there was a band called, The Grateful Dead.

Supposedly, on April 20th (some year between 65' and 75') the band was trying to buy some weed. They put together all the money they had on their persons at the time, and it amounted to $420. On April 20th, The Grateful Dead bought $420 dollars of weed, and after they realized the coincidence, they decided that in light of the "herbal" phenomenon, they would smoke before any/every show, at 4:20 PM because most Dead shows started around 5ish. During the show, the Dead would entertain their audiences with stories about what happened before the show, or just any stories that they had. They would usually include any crazy "Trips" or "Thoughts" they had while they were high. Normally, in the middle of someone's story, another band member would chime in and say "Yeah, but you weren't feeling that way until 420". Once the hippies caught on, it was just a spiral Up from there.