[thefabfive]

Not sure about archaic, but it doesn't seem to mean anything by itself.

Originally Posted by Wikipedia

Modern Russian: Hard sign
In modern Russian the letter ъ is called the hard sign. It has no phonetic value of its own, and is purely an orthographic device. Its function is to separate a number of prefixes ending in a consonant from a following morpheme that begins with an iotated vowel and is therefore written with one of the letters я, ё, е, or ю (that are pronounced as ya, ye, yo and yu only in Russian and Bulgarian languages). The hard sign marks the fact that the [j] continues to be heard in the composition. Example:

съёмка {{{1}}}(s'yomka) "filming"
Сёмка {{{1}}}(Siomka) male name derived from Семён (Simon)
It therefore functions as a kind of "separation sign" and has been used only sparingly in the aofrementioned cases since the spelling reform of 1918. The consonant before the hard sign often becomes somewhat softened (palatalized) due to the following iotation. As a result, in the twentieth century there were occasional proposals to eliminate the hard sign altogether, and replace it with the soft sign ь, which always marks the softening of a consonant. However, in part because the degree of softening before ъ is not uniform, these proposals were never implemented. The hard sign ъ is written after both native and borrowed prefixes. In recent years, it has sometimes been seen in borrowed words before the letter и, to mark a greater separation of the constituent syllables (the letter и does not mark an iotated vowel). Such written usage has not yet been formally codified (See also Russian phonetics and Russian orthography).