What I have liked in the past, is just using small, medium, large or unactionable.
Or with the right team/managment, not using estimates at all, just have people pick up the tasks they feel confident that they can get done within a given time frame after having the discussion in the group about differing opinions on complexity.
If you're looking to fill an arbitrary bucket, relative size matters most.
2 and 3 are equal. 5 and 8 are equal. The question is simply "Is this a couple days, the whole week, or the whole sprint?".
+ That's trivial, it will be ready for testing before lunch.
+ I know how to do that, should be ready tomorrow/next day.
+ I can see how to do that but there are lots of other constraints - at least a week, might be more.
+ It's a big project, needs more planning and specification before it becomes a series of estimable tasks. Let's do that.
+ That breaks other things we care about. We need to prioritize and be ready for rework.
If you want, you can call these small, medium and large.
Have a think and can you split it into two smaller tasks for the juniors to pick up.