noun
Vulgar slang for penis, used mainly by men and boys. Very informal; avoid in polite conversation.
男の子たちが「ちんこ」と言って笑っていた。
The boys were laughing and saying 'dick'.
noun
Kantō dialect word for practice or rehearsal. Rare and regional; not standard Japanese.
関東の一部では、練習のことを「ちんこ」と言うらしい。
In parts of Kantō, they apparently call practice 'chinko'.
The origin is uncertain. Possibly related to the childish word ちんちん, with the suffix こ (small thing).