to give strength, courage, or endurance to
to make (somebody or something) strong, e.g.:
to strengthen and secure (a place, etc) by military defences
to give strength, courage, or endurance to (somebody)
to add (e.g. alcohol to wine or vitamins to food) to strengthen or enrich it
to erect fortifications
fortifiable adj
fortifier noun
[Middle English fortifien via French from late Latin fortificare, from Latin fortis strong]