negligent

adjective
1
failing to give somebody/something enough care or attention, especially when this has serious results
سهل‌انگار, کاهل, بی‌مبالات, لاابالی
2
relaxed; not formal
بی‌خیال, راحت, شل گرفته, آسان‌گیر
He waved his hand in a negligent gesture.
her negligent grace
synonym nonchalant