deny, reject

(ことわる) The usual way to say reject or turn down.   $$$
(ひてい) Usually used with trials or politicians:He formally denied the allegations!
(きょひ) Absolute refusal. An exit line. Like if you tell a guy ‘no’ 10 times and he won’t go away, you use 拒否. ‘私がきょひした。’
(こばむ) The same as 拒否, but it can be physical as well as verbal. For example, if someone refuses to shake your hand, that’s 拒む。
ボツにする Publishing term. Turning down a manuscript or contribution. Shooting down an idea.
(きゃっか) Business term. An upper person turns down a proposal made by an underling.