Source: The Great Interpretation of Dreams (Ibn Sirin)
A mortar in a dream indicates a difficult man or a dispute and argument.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
A mortar indicates a woman of bad character. Pounding in it indicates falling into worry.
Source: Signs in the Science of Expressions (Ibn Shaheen)
A mortar is interpreted as worry. Whoever sees himself pounding in it will be afflicted with worry.