Mammoth Uncensored Word List:
19 - 17 letter words starting with st

standoffishnesses staphylorrhaphies stereochemistries stereolithography stereomicroscopes stereomicroscopic stereophotography stereoselectively stereoselectivity stereospecificity straightforwardly straightjacketing straitlacednesses stratigraphically stratospherically strongheartedness strongyloidosises structuralization structurelessness