First time I have come across an entry for an enemy Mebus in the diary of the 22nd Brigade RFA. . Apparently they are German Pill Boxes – i.e re article “...'Pill Boxes, or MEBUs as the Germans referred to'...
The diary page link for 16th July 1917 is https://talk.operationwardiary.org/#/subjects/AWD0003nyl
by ral104 moderator, scientist
MEBU stands for Mannschafts Eisen-Beton Unterstand, which translates as something along the lines of 'Iron concrete crew shelter'.