1. Expressing sorrow.

2. Expressing sorrow; mournful.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• ruffel,
• rageful,
• refur,
• resul,
• refun,
• refil,
• refule,
• hurful,
• refull,
• riteful,
• ruaul,
• trueful,
• ruraul,
• ueful,
• rurul,
• sueful,
• refual,
• refud,
• uefull,
• truful

• ruble,
• ruple,
• rubella,
• rubel,
• ruffle,
• ruefully,
• rubeola.

The adjective form of "rueful" is "ruefully".