Capable of being subscribed to; permitting subscription.(adjective)
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Use "subscribable" in a sentence
"But there are lots of things I follow that aren't subscribable by Amazon."
"That's why I consider Dave Winer's term for subscribable OPML files - Reading Lists - much too limiting."
"A new site called PolFeeds collects all of the online content produced by the presidential campaigns, Members of Congress, and the White House and makes it easily available and subscribable (aggregable?)."