The phrase "midweek loss" means a loss or defeat that happens during the middle of the week, typically referring to a sports match or competition. Full definition
The midweek loss was Arsenal's first away defeat for nine months, why should we think that suddenly we have become a bad team and will therefore lose another one this weekend? (justarsenal.com)
Henrikh Mkhitaryan and Pierre - Emerick Aubameyang are both in line to make their full debuts today, with the former only coming off the bench in the midweek loss to Swansea. (justarsenal.com)
First and foremost a return to the Champions League has to be prioritised, which can only be done with a top four finish or by winning the Europa League competition (as Manchester United did last year), but our current form, ignoring he midweek loss for our B side, I wouldn't rule us out pushing on to challenging for second place in the table, possibly even first once Manchester City finally start to show chinks in their armour. (justarsenal.com)