Adele and Jimmy Fallon Go Head-To-Head in Epic Game of 'Box Of Lies'

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Adele does not like to lose!

The singer's competitive side came out Monday night when she sat down across from Jimmy Fallon on The Tonight Show for a riveting game of Box of Lies.

The hit-maker's ability to bend the truth was put to the test and Jimmy wasn't about to let the "Hello" singer get away with anything.

WATCH: Adele Stuns With 'Hello' and New Single During 'SNL' -- See Video!

In the first round, Adele chose a box containing a T-Rex dressed up like a cowboy. Despite her clever approach at only lying about the dinosaur's costume (she said it was dressed like a fairy), Jimmy was able to see through her ruse.

Adele score an easy point when Jimmy lied about the contents of his box. What Jimmy got was a Simon Says game with fake noses glued to the buttons -- however, he didn't even try to explain it, and instead argued that it was a G.I. Joe doll dressed as Santa, getting attacked with a ninja star.

WATCH: Matthew McConaughey Dresses As Adele On 'SNL' and Saves Thanksgiving

Adele wasn't buying it at all, and an embarrassed Jimmy explained that the phallic nature of one of the prosthetic noses threw him off his game.

Then it was Adele's second turn, and this time she pulled from her box a stuffed giraffe with three donuts wrapped around its neck. This time, Adele went with the risky maneuver of telling the truth. After a tense tete-a-tete, it turned out she told the truth too well, and Jimmy could tell, thus winning the game.

"Bitch!" a disappointed Adele yelled at Jimmy, who couldn't believe his ears.

WATCH: Adele Says Drunk Tweeting Got Her in Trouble With Management

While she didn't win this round, the 27-year-old "When We Were Young" singer revealed that she always wanted to face off against Jimmy for a round of Lip-Sync Battle, which would be the most epic thing ever on TV.

After the tense showdown, Adele took to the Tonight Show stage and delivered a melodic, low-key performance of "Water Under the Bridge," a track off her recently released album 25.

MORE: 9 Times Adele Gave Us the Best Cry of Our Lives

If you never knew how truly funny Adele really is, check out the video below for a look at the world-famous singer posing as an Adele impersonator to pull a prank on other Adele impersonators!

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