Mukhālafat al-thiqāt means that a narrator transmits a report contrary to that of a more reliable narrator. This is an important reason for a report being unreliable.
This discussion has seven headings: mudraj, maqlūb, al-mazīd fī muttaṣil al-asānīd, muḍṭarib, muṣaḥḥaf/muḥarraf, shādhdh and munkar. Our focus now is mudraj.
1. Thiqah: a narrator reliable in integrity and preservation of reports. The comparison here is with a more reliable narrator.
2. The remaining names orient you to the discussion ahead; their definitions are not to be memorized here.