This is the 490th most frequent Icelandic word.
séð
"Seen."
In this sentence, 'séð' is the past participle of the verb 'sjá' (to see), used to indicate that the action of seeing has been completed.
Ég hef séð þetta hús áður.
I have seen this house before.
Here, 'séð' is used as part of the perfect form in conjunction with 'að hafa' (to have), indicating a completed action relative to another point in time.
Það er gaman að hafa séð þig.
It is nice to have seen you.
In this example, 'séð' again functions as the past participle of 'sjá', showing that the action of seeing the movie has not yet occurred.