Why this term exists
Local density alone cannot describe accumulated semantic/meaning structure. Meaning Mass provides an integration layer for comparing how much modeled coherent meaning is carried across a bounded interval.
Definition in the system
Meaning Mass is defined from Meaning Density rather than directly observed as physical mass. It belongs to the formal Semonika/Trajon modeling vocabulary.
The integration can include an additional factor S₂ that represents how local density contributes to a larger integrated structure. That factor requires explicit calibration for any empirical use.
Because the term borrows the word “mass”, public explanations must keep the model/metaphor boundary visible. The model can be useful without claiming equivalence to gravitational mass.
Example
A concept that attracts brief spikes of attention may have high local density at moments but lower integrated Meaning Mass than a concept that sustains coherent attention and relation over a long interval.