• firsat,
• ir's,
• fims,
• firy,
• virsu,
• hirs,
• forso,
• forsm,
• finers,
• fuirt,
• firsty,
• fierse,
• firmy,
• firsy,
• forse,
• firswt,
• furrs,
• firsco,
• girs,
• fies

• fires,
• first,
• firm,
• fierros,
• fire,
• airs,
• fibs,
• fir,
• fierce,
• fits.

The adjective form of the word "firs" is "fir".