break down
He tried to wink, a bad try, and I broke down and laughed.
my question is,

S1: We could say break down and cry.
S2: Could we say break down and laugh?

Does break down in S2 mean nearly the same as the one in S1?

Question

break down
He tried to wink, a bad try, and I broke down and laughed.
my question is,

S1: We could say break down and cry.
S2: Could we say break down and laugh?

Does break down in S2 mean nearly the same as the one in S1?

Answer

Yes.
"break down" means to change emotion, expression, stop maintaining an outward impression.
.
He looked serious for a moment, then broke into a laugh.