random
adjective
uk/ˈrændəm/ ushappening, done, or chosen by chance rather than following a system, plan, or rule:
random audits/checks/tests They discussed the idea of carrying out random forensic audits on listed companies as a deterrent to fraud.
The questionnaires are assigned on a random basis.
at random
without involving any system or decision:
chosen/drawn/selected at random The winner will be the first complete entry drawn at random after the closing date.