Part of Speech: Verb
Sob:Ā to cry or weep with convulsive catching of the breath
Source: Webster`s Dictionary
Found in,Ā āMy Boy WillieāĀ (line 27),Ā āAnd with every sob she let fall a tear,ā
The word sob is used in the poem to describe while the female(subject) was crying, she was taking repetitive breaths.