WBR (Word BReak) tags offer the browser an option to insert line breaks within a word instead of only in between words. E.g. in Einstein-(wbr)Rosen-(wbr)Bridge the browser could insert a line break after either dash, so that the lines are filled out better. It's a not well-known, but perfectly normal HTML-tag as specified by the W3C.
My site is http://www.roachware.org, and the tags get sprinkled into the articles at random places. In the example above, it might turn out like Ei(wbr)nstei(wbr)n-Ro(wbr)sen-Brid(wbr)ge - a line break at any (wbr) in the second example looks extremely sloppy.