The phrase "for a second" can be replaced with numerous synonyms to convey the same meaning. Some of the most common replacements include "momentarily," "briefly," "temporarily," "fleetingly," or "transiently." These words all express the idea of something happening in a short amount of time without being permanent or long-lasting. Depending on the context, other options for synonyms might include "instantly," "momentarily," "moment by moment," or "for an instant." Whether you're speaking, writing, or just thinking about time, having a wide range of synonyms for "for a second" can help you better convey your message in a more varied and nuanced way.