To Be Mixed
To Be Blended With, To Join
intransitive verb, godan verb
You know that 交ぜる means to mix and that the kanji means mix as well. So, this probably has something to do with mixing things. This word means to be mixed. This is when something is mixed but it's not mixed by you. It's just being mixed. Think of it this way - the じ in 交じる is Jesus, who just uses Jesus magic to mix something. So, you're not mixing it. It's just when something is to be mixed.
The reading is the same as with 交ぜる. So long as you know the ま portion of that word's reading, you'll be able to read this word as well.
白い毛の中に黒い毛が交じる。
Black hair is mixed in with the white hair.
コンビニで買ったサンドイッチに毛糸が交じっていた。
Some wool yarn was mixed in with the sandwich I bought at the convenience store.
たくさんの日本人の中に交じって今日も生きています。
Today I live among many Japanese people.