A phrase used to determine the appropriate circumstances under which to flush a toilet. Urine was to be left unflushed in the toilet bowl while feces were to be flushed right after bowel evacuation. This was used in efforts of water conservation either in the sense of environmental conservation or the saving of clean toilet tank water during power outages in remote areas.
“Man, don’t waste three gallons of water to get rid of a cup of sterile piss.”
“Why is that kindly hippy?”
“Just remember man, 'If it’s yellow, let it mellow. If it’s brown flush it down.'”
“Thank you, sir. Perhaps with the water we save in the crapper you might be able to bathe more thoroughly in the future.”

If it's yellow, let it mellow. If it's brown, flush it down
by Capt. Chunkstyle May 08, 2006
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to be a coward, to be cowardly
You obviously have a yellow streak down your back.
by Light Joker April 25, 2006
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a slang term that Pokémon fans use for "lets rob that bank over there"
Brian: hey Lucas, yellow squirtle keezy megaevolution ultraforms unite
Lucas: yeah nigga lets do it.
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black and yellow flying things with stingy stings is another word for a wasp or a bumble bee.
ahhhhhhhhh! black and yellow flying things with stingy stings are everywhere, stupid cunts
by NatalyaBranigan October 03, 2021
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The seven colors of the rainbow, also the same colors of the pride flag for LGBTQ.
Dude 1: What are the colors of the rainbow.
Dude 2: Umm.. it's red orange yellow green blue indigo violet.
Dude 3 in the corner: HAHA! YOU GAY!
by BlackSoul659 March 05, 2022
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green, funkyfunk, funkeefunkee, HERBal tea, dat primary concoction,
"what you get when you mix blue and yellow?"
"dat supa green"
"don't forget the red hairs"
by im glenjamin December 04, 2006
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