The term NATO Alphabet Letter in 'NATO' is solved by the crossword answer OSCAR, which is a five-letter word. The NATO Alphabet, also known as the International Radiotelephony Spelling Alphabet, is a system of words used to represent letters of the alphabet in order to facilitate communication between two or more parties. The NATO Alphabet was created by the North Atlantic Treaty Organization (NATO) and is used by military personnel, police, and other emergency services. The letter O in the NATO Alphabet is represented by the word OSCAR.