Definition from Wiktionary, the free dictionary
The final -mu is cognate with conjectural む (mu).
らむ (romaji ramu)
- conjecture about a presently occurring situation that the speaker has no direct knowledge about
- conjecture about the cause or reason of a presently occurring situation that is directly observed by the speaker
- hearsay based on things heard or read
- らん (ran)
- らし (rashi)