The phrase "fall back on" is mostly used to describe a situation when someone has no other choice but to rely on a certain thing or person. However, there are several synonyms to this phrase that can be used interchangeably in different contexts. Some of these synonyms include "resort to," "lean on," "rely upon," "turn to," "depend on," and "fallback." Each of these synonyms has a slightly different connotation, but the main idea remains the same - in times of trouble or uncertainty, we tend to rely on certain things or people to support us and help us get through difficult situations.