—v.t. 1. to protect or strengthen against attack; surround or provide with defensive military works.
2. to furnish with a means of resisting force or standing strain or wear: to fortify cotton with nylon. 3. to make strong; impart strength or vigor to: to fortify oneself with a good breakfast. 4. to increase the effectiveness of, as by additional ingredients: to fortify a diet with vitamins; to fortify a lotion with lanolin. 5. to strengthen mentally or morally: to be fortified by religious faith. 6. to confirm or corroborate: to fortify an accusation with facts. 7. Nutrition.to add one or more ingredients to (a food) to increase its nutritional content.
8. to add alcohol to (wine or the like).
—v.i. to set up defensive works; erect fortifications.