His actions were extremely out of line during the event.

out 在这里表示"超出"的意思。 of 是介词，表示所属关系或范围。 line 本义是"线"，引申为"界限、规范"。 out of line 是一个固定短语，意思是"越界、失礼、不合规矩"，指行为超出了可接受的界限或规范。