Sadly abbr with title doesn't work at all on mobile Chrome [1] or Firefox [2]. Probably not Safari either, since long press on mobile means "select text" so you'd have to do some CSS trickery (and trying to hit a word-sized target with a finger is quite annoying).

[1] https://issues.chromium.org/issues/337222647 -> https://issues.chromium.org/issues/41130053

[2] https://bugzilla.mozilla.org/show_bug.cgi?id=1468007