mediocre talent; ordinary ability
A somewhat literary or formal term for a person of average or unremarkable talent. Often used self-deprecatingly or in contrast to 天才 (genius).
彼は自分を庸才だと言って、いつも努力を惜しまない。
He calls himself a person of mediocre talent and never spares any effort.
天
The difference between a genius and a person of ordinary ability lies in accumulated effort.
Composed of 庸 (ordinary, commonplace) and 才 (talent, ability). The exact historical derivation is uncertain, but the kanji combination directly conveys the meaning of 'ordinary talent.'