広まる
ひろまる · hiromaru · JLPT N3 · verb-godan
to spread
📢 広 hiro = wide (広い hiroi) + -maru: to become wide, so it spreads
広 is the kanji in 広い (hiroi, wide). The ending -maru makes it intransitive: something spreads on its own, like a rumour or a custom. Its transitive partner is 広める (hiromeru), to spread something yourself.