expression, godan verb (-ru)
join in; get in on; have a share in
Idiomatic expression meaning to participate in a plan, business, or activity, often with the nuance of getting a share of the benefits or profits. Commonly used in informal contexts.
彼もその儲け話に一口乗った。
He also got in on that money-making scheme.
面白そうなプロジェクトだから、私も一
It sounds like an interesting project, so maybe I'll join in too.