Wiktionary
conj. (context idiomatic English) then again, on the other hand; used to show that the opposite viewpoint is possible.
WordNet
adv. (contrastive) from another point of view; "on the other hand, she is too ambitious for her own good"; "then again, she might not go" [syn: on the other hand, then again] [ant: on the one hand]
Usage examples of "but then".
My father started working on this idea years ago, but then natural rubber was so cheap that it didn't seem worth going on with.
I thought he might make me hurt myself again, but then Herb stepped in front of me and told, him the same thing, to go away and calm down and then come back and maybe we could help him fix whatever was wrong.
For a moment it seemed they would go into the living room together, but then Susi pulled away.
I didn't even hear the TV go off Tak & Seth had been having a MotoKofs 2200 festival most of the day but then a, shadow fell over me and I looked up and there he was.
At first I thought it was Tak Seth has been mostly gone this last week, or lying low but then I saw the eyes.