Definition of swallow noun from the Oxford Advanced American Dictionary

Oxford3000

swallow

noun
/ˈswɑloʊ/
 
 

bird

1 a small bird with long pointed wings and a tail with two points, that spends the winter in warm parts of the world but flies to northern countries for the summer

of food/drink

2 an act of swallowing; an amount of food or drink that is swallowed at one timeShe took a swallow of coffee.
IDIOM

one swallow doesn't make a summer

(saying) you must not take too seriously a small sign that something is happening or will happen in the future, because the situation could changeone swallow doesn't make a summer