convulse vs thrash about

convulse and thrash about both are verbs.

Word	Noun	Adjective	Verb	Adverb
convulse	No	No	Yes	No
thrash about	No	No	Yes	No

As verbs, convulse and thrash about are synonyms defined as:

Other synonyms of convulse include jactitate, slash, thrash, thresh, thresh about, toss.

convulse (verb)	thrash about (verb)
be overcome with laughter	move or stir about violently
make someone convulse with laughter
contract involuntarily, as in a spasm
cause to contract
move or stir about violently
shake uncontrollably