The Dutch word for mouth is
mond

Dutch Definition

mouth
1. mond, bek

bek
1. n-m. a bird's beak
De raaf had een stuk kaas in zijn bek. - The raven held a piece of cheese in its beak.
2. n-m. any animal's mouth (such as a snout)
3. n-m. (informal, rude) a human mouth
Hou je bek! - Shut your trap!
4. v. first-person singular present indicative of bekken
5. v. imperative of bekken

muil
1. n-m. An animal's mouth and muzzle or snout
De hond kauwde op het bot met zijn muil. - The dog chewed on the bone with its muzzle.
Hij opende de muil van de hond om te kijken naar zijn tanden. - He opened the dog's mouth to look at its teeth.
De varkenszuster was bedekt met modder tot aan haar muil. - The pig's snout was covered with mud.
2. n-m. (pejorative) A person's face
3. n-m. (notably in muilen trekken) A funny, angry ... face one makes, facial expression
4. v. first-person singular present indicative of muilen
5. v. imperative of muilen
6. n-m. (usually as plural diminutive muiltjes) A flat type of footwear
De sprookjesprins zocht Assepoester met als enige aanwijzing haar glazen muiltje
The fairytale prince looked for Cinderella with her glass slipper as the only clue
7. n-m. A mule, an equine crossbreed between a stallion (horse) and a she-ass (donkey)