"Bitcoin forums" refer to online communities or platforms where people gather to discuss and exchange information about the cryptocurrency called Bitcoin. Full definition
«Imagine there was a base metal as scarce as gold,» the inventor wrote in a thread on an online Bitcoin forum. (fortune.com)
«This was already apparent in Satoshi's white paper, emails, and his discussions on bitcoin forums where he expressed similar views,» explains Mr. Wu's translated interview. (ccinews.net)
Indeed, after XRP Ledger (then called the Ripple Consensus Ledger) was created, XRP tokens were distributed to users of popular bitcoin forums in what isn't all that different from what's today called an «airdrop.» (coindesk.com)