1. past tense of proof; checked or tested for errors, accuracy, or quality
2. past tense of proof; made resistant to something (water, fire, etc.)

Examples

• The editor proofed the manuscript before publication.
• She proofed the math problems twice to catch any mistakes.
• The fabric was proofed against water damage.
• He proofed the document for spelling errors.
• The tent material had been proofed to resist rain.
• The proofreader proofed all the galleys yesterday.
• They proofed the leather jacket to make it waterproof.