1. Something to make a substance more stiff.

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

• stifeling,
• stiffining,
• stifening,
• stiffling,
• stiffeling,
• stuffering,
• stifleing,
• stiffiling,
• atiffening,
• stiffning,
• stiffenning,
• stiffeningg,
• stifning,
• stiffinng,
• selfdening,
• stiffenins,
• stiffennigs,
• stiffennings,
• Skiffeling,
• skiffering

• steffens,
• stiffener,
• stiffen,
• stuffing,
• steffensen,
• Steffenhagen,
• stuffing nut,
• stiffened,
• Steffen,
• Stefanie,
• Stefania,
• Stephenie,
• Stefaniak,
• Stefani,
• stefanik,
• Steffanie,
• stuffing box,
• Steffenson.

The adverb form of the word "stiffening" is "stiffeningly".

The adjective form of the word "stiffening" is "stiffened".

The plural of the "stiffening" can be the "stiffenings".

The singular of the "stiffening" can be the "stiffening".