<span class="searchmatch">submilliarcsecond</span> (not comparable) Smaller than one milliarcsecond...
sub-milliarcsecond (not comparable) Alternative form of <span class="searchmatch">submilliarcsecond</span>....
unit of angle equal to one thousandth of an arcsecond (used especially in astronomy) (abbreviation): mas, milliarcsec <span class="searchmatch">submilliarcsecond</span> milli- arcsecond...