  We report the discovery of a unique object in the MeerKAT Galaxy Cluster
Legacy Survey (MGCLS) using the machine learning anomaly detection framework
Astronomaly. This strange, ring-like source is 30' from the MGCLS field centred
on Abell 209, and is not readily explained by simple physical models. With an
assumed host galaxy at redshift 0.55, the luminosity (10^25 W/Hz) is comparable
to powerful radio galaxies. The source consists of a ring of emission 175 kpc
across, quadrilateral enhanced brightness regions bearing resemblance to radio
jets, two "ears" separated by 368 kpc, and a diffuse envelope. All of the
structures appear spectrally steep, ranging from -1.0 to -1.5. The ring has
high polarization (25%) except on the bright patches (<10%). We compare this
source to the Odd Radio Circles recently discovered in ASKAP data and discuss
several possible physical models, including a termination shock from starburst
activity, an end-on radio galaxy, and a supermassive black hole merger event.
No simple model can easily explain the observed structure of the source. This
work, as well as other recent discoveries, demonstrates the power of
unsupervised machine learning in mining large datasets for scientifically
interesting sources.
