"Running by" is a common phrase used to describe a fleeting moment or passing of time. However, there are various synonyms that can be used to describe this action. For example, the phrase "passing by" can be used to convey the same meaning. "Rushing past" or "zooming by" can also be used to describe something moving quickly. Additionally, "fleeting," "transient" or "ephemeral" can be used as adjectives to describe the passing moment. Each of these synonyms can be used to add depth and variety to communication, allowing for a more nuanced understanding of the concept of passing time.