The Acrobat is the second largest member of the bat family. They are typically entertainers whose routine revolves around feats of great dexterity, such as climbing, swinging, tumbling, walking across ropes strung between high points, turning flips and so forth. It's a very physically demanding form of entertainment that requires tremendous coordination and grace.
Acrobats have appeared several times in the setting of Dungeons & Dragons; the first Acrobat was an experimental variant class for Advanced Dungeons & Dragons 1st edition, which debuted in the original Unearthed Arcana. Closely tied to the Rogue, it didn't catch on, but a second attempt was made through the Kits system in AD&D 2nd edition, where it was once again depicted as a thief specialized in climbing and tumbling.
After this less than impressive outing, the acrobat disappeared as a class. Although in 3rd edition, at least, a high-Dexterity Bard with proficiencies in the right skills could easily be played as an acrobat. Also 3.5 offered the Swashbuckler, a lightly-armoured dextrous fighter; in parallel Arcana Unearthed lifted, from Stephen Donaldson, the Unfettered.
The Acrobat is mostly known to the D&D fandom for the fact it was used as one of the character classes to appear in the D&D Cartoon, alongside fellow Unearthed Arcana classes Barbarian and Cavalier. The character's official 3.5 stats made her a Monk.
Given his fondness for nostalgia shilling, Mike Mearls made an announcement on his livestream of what an Acrobat subclass for the Rogue looks like in his own personal campaigns. It hasn't seen print yet, but it has been put down on the 5etools website; it gives your rogue the following features:
- Aerial Artistry (3rd Level): When you move, you can instead take two short movements by flying. Each movement is half your speed, and you must end each one on a solid object or the ground. If you do not, you fall and your movement ends.
- Fearless Aerialist (9th Level): You no longer take damage from falling.
- Unchained Agility (13th Level): You are permanently under the effects of a Freedom of Movement spell.
- Aerial Mastery (17th Level): When you move, you can instead take four short movements by flying. Each short movement is still limited to half your speed, and between each movement you must still touch a solid object or the ground. If you do not, you fall and your movement ends.