Dreaming of a deceased mother expressing anger can be a deeply emotional experience. Such dreams often reflect unresolved feelings, guilt, or issues related to your relationship with her. Here are a few interpretations to consider:

1. Unresolved Emotions: This dream may indicate that there are unresolved feelings or regrets regarding your relationship with your mother. It could be beneficial to reflect on any lingering issues or unexpressed emotions you may have.
2. Self-Criticism: Sometimes, a dream of a loved one being angry can symbolize your own feelings of guilt or self-criticism. You might be judging yourself harshly for decisions or actions in your life.
3. Fear of Disapproval: If you often seek approval from your mother, her anger in the dream could represent your fear of not living up to expectations, either from her or from yourself.
4. Processing Grief: If your mother has recently passed away, the dream may be a way for your subconscious to process your grief. Emotions can manifest in various forms in our dreams, and anger may come up as part of this process.

Consider what specific feelings or situations in your waking life might be connected to this dream. Journaling or talking about your feelings with someone you trust can offer additional clarity and help you work through any unresolved issues.