What is the meaning of 太政官?

the highest governing body under the 律令 (Ritsuryō) system between the Nara and Edo periods

Same as だじょうかん (Dajō-kan) below

the highest governing body of Imperial Japan in the early Meiji period

Same as だじょうかん (Daijō-kan) above

the highest governing body under the 律令 (Ritsuryō) system between the Nara and Edo periods

Synonym of 太政大臣 (ōki ōimōchigimi): the head of the Ōimatsurigoto no Tsukasa, equivalent to a “grand minister” or “chancellor of the realm

the highest governing body under the 律令 (Ritsuryō) system during and after the Nara period

Source: wiktionary.org