訴願 is read as そがん (sogan) and means petition.
そがん
sogan
そがんにん
petitioner
あいそたんがん
plea
うったえ
lawsuit
そしょう
litigation
うったえる
to complain
そじょう
petition
そつい
impeachment
そにん
a suitor
そついいいんかい
indictment committee
そきゅうりょく
appeal (e.g. of an advertisement)
うったえでる
to lodge a complaint
そがい
party not named in (this) court case