Bash up Definition 1 of 2Pro Tip 1/3Violent Connotation This usage implies physical violence; it's often associated with aggressive behavior. Avoid altercations; you might end up getting bashed up. Pro Tip 2/3Informal Speech 'Bash up' is informal and more common in casual or conversational contexts. In formal situations, say 'assaulted' instead of 'bashed up.' Pro Tip 3/3Passive Structure Often used in the passive voice to indicate the person receiving the action. He got bashed up by a group of instigators last night.