without a by your leave
without so much as a by-your-leave
dated Without asking for permission. The phrase implies that the speaker is frustrated or exasperated by what has been done. He borrows my car without so much as a by-your-leave, and I'm supposed to thank him for bringing it back in one piece? I don't think so.
without (so much as) a (for or) by your leave
without (the least hint of) asking for permission. Without so much as a for or by your leave, they just walked into our house. He left, without a by your leave.
without (so much as) a ˌby your ˈleave(old-fashioned) without asking permission; rudely: What do you think you’re doing, coming in here without so much as a by your leave?
Leave in this phrase means ‘permission’.