No. "Meantone" means the tuning has been adjusted so the pitch produced by either Bb or A# is the average (or the 'mean') of the two pitches. You end up with just 12 pitches per octave, just as you do in equal temperament.
EDIT: The OP has requested I elaborate on my answer, which I see has gotten a number of downvotes. Perhaps that’s deserved – as a music teacher I shade answers to the perceived level of what a student knows (e.g. in teaching a time signature “the top number is the number of beats per measure” is sufficient, and a discussion of simple vs compound meters waits until later).
With that out of the way…
Keyboard instruments prior to about 1500 had as many as 19 keys per octave, with split keys for all of the modern black keys, plus a B# and E# that were different from C and F. (See the first photograph in http://www.harpsichord.org.uk/wp-content/uploads/2015/04/archicembalo.pdf for a reproduction of an early 16th century archicembalo with 19 keys per octave in the lower manual.)
The large number of keys was required by Pythagorean tuning: as you go up the harmonic series you get different pitches for F#/Gb etc.
Manufacturing technology was improving quickly in the 16th century, with new techniques for pulling wire (the strings in most of these instruments were drawn brass). As a result, we were now capable of making instruments with a larger range. Even in Pythagorean tuning that means bumping up against the Pythagorean comma: three pure 5:4 thirds do not add up to a 2:1 octave. The larger the range of the instrument, the more pronounced the discrepancy.
Concurrent with this was a desire to make instruments simpler, reducing the number of keys. This would make them both easier to manufacture and easier to play.
Solving the Pythagorean comma at a practical level was needed. The earliest solution that I know of was that of Pietro Aron in his book Toscanello in musica published in 1539: he proposed dividing the comma into four parts, and lowering the tuning of four consecutive fifths by that amount to create a perfect octave while retaining most of the pure thirds. His system resulted in eight pure thirds and four that were terrible (wide by about 40 cents). The fifths were narrow by about six cents, except for one – that was wide by a whopping 35 cents. In case you’re interested in looking into it in depth, the tuning portion of his book is online in translation at http://www.tonalsoft.com/monzo/aron/toscanello/aron_toscanello.htm
Using Aron’s tuning made it possible to create an instrument with 12 keys per octave that sounded at least acceptable in a number of keys. Keys that required the bad notes, known as “wolf tones” were avoided.
Aron’s method came to be known as meantone tuning. Tempering for two consecutive fifths meant that the major second interval was halfway (the mean) to the major third. Give or take 1/10th of a cent, which is certainly close enough for the purpose. Any tuning that results in equal whole steps can properly be called meantone, and meantone tunings can be created by using 1/3 of the comma, or 1/5th, or any other fraction less than the number of discrete pitches per octave (our 12TET system is one variety of meantone).
The development of meantone tuning was concurrent with the elimination of split accidentals, or at least as concurrent as the speed of information traveling in the 16th century would allow. This meant it also had the effect of adjusting the black keys to fall between the Pythagorean sharp and flat pitches.
In the context of the question, my original answer – that meantone split the difference between sharps and flats – is accurate. The fact that you can have meantone tunings with divisions of the octave other than twelve is true… but I judged it irrelevant to the question.
The next problem was how to handle the wolf tones. Many tuners devised adjustments to meantone tuning to reduce or eliminate the wolves by raising or lowering specific pitches. Werkmeister was one of them, and devised a number of possible tunings. These tunings are called well temperament, because it allowed the instrument to play well in all keys.
Because well temperament results from the adjustment of individual pitches you end up with intervals that are not all the same size. Your minor third in C will be different from your minor third in D or Ab. Some found this a feature rather than a bug: each key now had its own unique character, distinct from any other key. Various well temperaments stuck around through the 1800s, and are still used by “period” instrumentalists.
12TET began to replace well temperament in the mid 19th century, and is considered the standard today.