Metasearch is described as 'Search aggregator for Slack, Google Docs, GitHub, and more'. There are six alternatives to Metasearch for a variety of platforms, including Online / Web-based, Windows, Linux, Mac and Self-Hosted solutions. The best alternative is elasticsearch, which is free. Other great apps like Metasearch are Algolia (Free Personal), Apache Solr (Free, Open Source), wordpress i-search pro (Paid) and Tribus (Freemium).
Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and JSON APIs. Its major features include powerful full-text search, hit highlighting, faceted search, dynamic clustering, database integration, and rich document handling.
Enterprise search, simplified. Cloud-based enterprise search solution that search across all of your organization’s content sources — Aconex, Procore, Dropbox, Microsoft Sharepoint, Onedrive, and more.