DBMS_REDEFINITION don't copy data? Is there an option to use Oracles online table redefinition feature but only copy a subset of the data from the source table?

I mean - the source table has 2M records and I want to only copy those that have ID > something. The problem is that START_REDEF_TABLE seems to sync all 2M records. Is there a way how to specify whics records should be synced over?
If I understood you don't need to do it online. 

In this case, how about a CREATE TABLE AS SELECT using a select which is focusing on the subset of data?

Then you just do a quick rename, recreate the indexes and done.