Orange blossom water
A clear, fragrant distillate of bitter orange blossoms that gives sweets and drinks a floral note.
Orange blossom water is sold in Turkish, Arab or Persian grocers, often in the baking aisle of larger supermarkets, at pharmacies or by mail order. There is no true equivalent; rose water or grated orange zest come closest but change the character.
Substitute:
There is no real substitute. Rose water is similarly floral but tastes clearly of rose rather than orange blossom; finely grated orange zest adds citrus freshness but not the floral scent.