Wiktionary
vb. (context intransitive English) To participate, take part or get involved in something.
Usage examples of "join in".
Her temperament was not theirs so she could not join in the wild laughter.
When he did, it was a joyous experience for his friends, compelling them to join in.
They would do it piecemeal, leaving the pikes and the Cairhienin horse behind, though the Cairhienin might join in once they realized what was happening.
Ranger One says that's because Earth is as much in danger from these Shadows as Minbar, so we have a responsibility to join in the fight.
Many elves died repelling the invaders, more than should have, I fear, since their king was too busy to join in their fight.
Cadderly knew that he could not afford to delay much longer, that he should join in the fight beside his friends, and that even if he did not, the battle would likely come to him all too soon.
At that moment Govannan called out, urging Conn to join in the new dance.
When the Lizards are dealt with, we can join in punishing the inhabitants of that land to the full extent they deserve.
You will have to join in the singing without singing, nobody eats.
If you hold fast to the man that you are, you will yet join in that sharing, I promise you.
Since there was no longer any ship for Enomoto to pilot, he was ordered to join in the ground defense.