The phrase "running out" implies that a resource or time is dwindling, and may soon be exhausted. Synonyms for this phrase include "decreasing", "diminishing", "fading", "waning", "ebbing", "dwindling", "shrinking", "sinking", "lessening", and "falling short". These words all convey a sense of scarcity or limited availability. For example, you might say that your patience is dwindling during a long wait, or that your budget is shrinking as expenses pile up. No matter the context, using synonyms for "running out" can add nuance and variety to your language, making your writing more engaging and effective.