thrower vs throwster

thrower and throwster both are nouns.

Word	Noun	Adjective	Verb	Adverb
thrower	Yes	No	No	No
throwster	Yes	No	No	No

As nouns, thrower and throwster are synonyms defined as:

thrower and throwster: a person who twists silk or rayon filaments into a thread or yarn

thrower (noun)	throwster (noun)
someone who projects something (especially by a rapid motion of the arm)	a person who twists silk or rayon filaments into a thread or yarn
a craftsman who shapes pottery on a potter's wheel and bakes them in a kiln
a person who twists silk or rayon filaments into a thread or yarn