Still concurrent (2,3,4,4)
I believe the answer is:
at the same time
I believe this is a double definition.
'still' is the first definition.
(thesaurus)
'concurrent' is the second definition.
('at the same time' can be a synonym of 'concurrent')
(Other definitions for at the same time that I've seen before include "nonetheless" , "together" , "on the other hand" , "Coincidentally - still - however" , "Simultaneously - nevertheless" .)