If you translate directly, the result should be "Tarnishing the lowest seat.".
I use this phrase when I have to explain the position of my Bugei often.
The meaning of this phrase is simply "I am the member of (this group)".
I would like to add a few more explanation to this phrase for all of my Buyu.
There is no seat for ordinary disciples. The seat is only for instructor grade.
For Japanese, "Having the seat", it self is good enough to showing off your authority to others. As you already know that showing off any kind of superior point is just extreme shame behavior in Japan.... We believe "superior point" is only for doing for others, never for showing. That is the reason to use "lowest" seat. Even if a disciple is oldest or highest disciple, truly superior disciple will use "lowest seat" for his self introduction.
There is no verb of "sitting" in this phrase. "lowest" is not enough to negate such as you high pride! Superior disciple know that the seat in the dojo is not for sitting. Or sitting the seat for relaxing in the dojo is shame. And superior disciple know that it is presumptuous to sit with other instructors grade. That is why "tarnishing" is used.
"Boasting tree" is really grow up so quickly. When we realize to prune it, mostly it is late. And often, "Boasting tree" kill the owner... Japanese culture have lot of the safety lock of this kind of thing.
I always want to be "Tarnishing the lowest seat." in the dojo.
Also, these two poems are also my favorite. Please consider about it for your Bugei;
稔る程 頭を垂るる 稲穂かな
"When the ear of rice is growing up, the head becomes hanging down deeply."
下がる程 その名は上がる 藤の花
"When the wisteria flower grow lower, it becomes higher grace."
SD101231 FUDOAN HEKISHISAI