Meaning "less than something should be". It's the opposite of "overly".
It's one of those words that you know isn't necessarily proper English, but you still find slipping into your sentences every so often.
I am so underly protective, but I know my girl won't mess around
by marrymenow December 30, 2015
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1. For something to be under/situated under something
2. Something that is important, but is hidden away
1. There is an underlying issue with this program. (There is an issue that is not obvious with the program)
2. A green box is underlying another box. (A green box is underneath another box)
by FesterTY September 14, 2018
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An underlying slopper is the act of a girl smearing her boyfriend's diarrhea on his balls and then using said diarrhea as lube to give him a handjob.
Man, I just got an underlying slopper from my girlfriend. It was fucking arousing and awesome!
by MonsterLog42 December 11, 2022
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(FINANCE) a stock whose price movements determine the value of a financial derivative. For example, when a hedge fund manager writes a call option for Citigroup (NYSE:C) at 4.25/share, C is the underlying stock.

"Underlying" can be used to refer to other things besides stocks; for example, commodities, currencies, or bonds.
A put option rises when the spot price of its underlying stock declines.
by Abu Yahya April 5, 2010
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the dark matter that builds up uner your toenail after 3 months of avoidance, not to mention it smells like rotten mayo the dwells in liklyness of teste satchel.
you smell like the underlying filth , i want to kill my whole family
by oren November 6, 2004
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A Covid-denier's first response to hearing that a person has died from Covid-19. Because they absolutely know that the disease is nothing more than a politicized hoax.
"My friend died from Covid."
"She must have had underlying condition."
by Monkey's Dad September 7, 2020
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