v.1. To give ground; retreat: After an unsuccessful attempt to retake the city, the soldiers fell back.
2. To recede: The waves fell back, leaving frothy white bubbles on the sand.
3. fall back on To use something as a substitute or backup: If we run out of cash, we will have to fall back on the money in our savings account.
4. fall back on To rely on someone or something for support: At least I can fall back on my friends in times of need.