"MTBoS" (variant, "MTBOS") is an acronym for "Math Twitter Blogosphere" and is used by some mathematics educators on Twitter use to describe their community. The term is often used as a hashtag on Twitter ("#MTBoS") in order to make tweets of the community more visible and searchable.
History of "MTBoS" Acronym
The term "twitterblogosphere" was used as early as 2010 to describe an emerging online community of math educators (https://twitter.com/jybuell/status/19270779491). Other variants included "blogotwitterversphere" (http://samjshah.com/2010/06/30/blogotwitterversphere/).
"Mathblogosphere" (https://twitter.com/nik_d_maths/status/271309095515070465) and "Math Twitter Blogosphere" (https://twitter.com/j_lanier/status/227965292150669312) were in use by 2012. Other variants included "Math Blogotwittosphere" (http://blogs.edweek.org/edweek/edtechresearcher/2012/07/the_math_blogotwittosphere_is_the_best_blogotwittosphere.html).
The first use of the acronym was in 2013 by Christopher Danielson:
I do wonder how collective wisdom of mtbos could be brought to this larger audience. Answer may just be time.