1) Discourteously abrupt 2) Forgoing formality 3) Hasty 4) Informal 5) Unceremonial 6) Without ceremony or formality 7) Without due formalities Found on https://www.crosswordclues.com/clue/unceremonious
discourteously abrupt; hasty; rude: He made an unceremonious departure in the middle of my speech. · without ceremony or formalities; informal. Found on https://www.infoplease.com/dictionary/unceremonious