We don't have synonyms for blowby yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are blowzy, blobby and blowy.
(n) :
Alternative spelling of blow-by. [(automotive) In an internal combustion engine, any burnt or unburnt matter escaping from the cylinder, past the (worn) rings on the piston, and into the crankcase.]
(n) :
Alternative spelling of blow-by. [(automotive) In an internal combustion engine, any burnt or unburnt matter escaping from the cylinder, past the (worn) rings on the piston, and into the crankcase.]