fortify

(verb) make strong or stronger. Synonyms: strengthen, beef up. Examples: "This exercise will strengthen your upper body." "Strengthen the relations between the two countries."

(verb) enclose by or as if by a fortification. Synonyms: fort.

(verb) prepare oneself for a military confrontation. Synonyms: arm, build up, gird. Examples: "The u.s. is girding for a conflict in the middle east." "Troops are building up on the iraqi border."

(verb) add nutrients to. Examples: "Fortified milk."

(verb) add alcohol to (beverages). Synonyms: spike, lace. Examples: "The punch is spiked!."