Matri Dosha occurs when the Moon is placed in a malefic house (the 6th) or the house of the enemy; it causes distress to the mother, and is pacified by chanting and worship.
Verse 2 — Moon in the Fourth Afflicted by Malefics
चन्द्रः शनिना भौमेन राहुकेत्वा च पीडितः ।
चतुर्थस्थो भवेद् यस्य मातृदोषः स उच्यते ॥
candraḥ śaninā bhaumena rāhuketvā ca pīḍitaḥ |
caturthastho bhaved yasya mātṛdoṣaḥ sa ucyate ||
If the Moon placed in the fourth house is afflicted by Saturn, Mars, Rahu or Ketu, that condition is called Matri Dosha.