BIN$ objects

Object names starting with BIN$ are related to recycle bin. Whenever an object (table, index etc)is dropped, an entry is created in recycle bin with name starting with BIN$, if that is enabled forthe database. They show up in

select * from recyclebin;
or
show recyclebin

If you do not want dropped tables to go to recyclebin and be deleted permanently you should use

DROP TABLE myTable PURGE;

To purge recyclebin you should login as that user and use the command:

purge recyclebin;

To purge the recyclebin of all users login as SYS or SYSTEM and issue the command:

purge dba_recyclebin;