* It's a misspelling: Perhaps you meant a different word, like "sign," "signal," or "swagger."
* It's a regional slang term: Some words have very localized meanings. If you heard it used somewhere specific, try asking people from that area.
* It's a made-up word: Someone might have created it for a fictional story, game, or other purpose.
Could you provide more context about where you encountered the word "sigwan"? That would help me figure out what it might mean.