川柳 (senryû) are simplified 俳句 (HaiKu). There is no obligation to insert a season word and there is no rule concerning the 切字 (KireJi). At first the 川柳 (SenRyû) “Senryû” were mostly indecent poems and were called 狂句 (KyôKu) “devil + verse”. The main theme for Senryû is the humand nature and all its weaknesses. The style is concise, humorous, subtle or satiric.
Since 1987, the 第一生命 (DaiIchiSeiMei) group (life insurance company) hold a yearly Senryû competition called サラリーマン川柳コンクール “the Senryû contest by 'salary men'”.
Some examples from this contest can be found in the blog: サラリーマン川柳 (SaRaRI-Man SenRyû) (2004) et Senryû par des salariés [fr] (2006).