Definition of onion noun from the Oxford Advanced Learner's Dictionary

Oxford3000

onion

noun
ˈʌnjən
 
; ˈʌnjən
 
[countable, uncountable]
 
a round vegetable with many layers inside each other and a brown, red or white skin. Onions have a strong smell and flavour
Chop the onions finely.French onion soup