1. Semantic Bleaching: This is the most common term and refers to the gradual loss of meaning in a word, often leaving it with a more general or vague meaning. For example, the word "awesome" once meant "inspiring awe," but now it's used for anything considered good or enjoyable.
2. Semantic Shift: This term describes a change in the meaning of a word, often through a process of metaphor or metonymy. While not necessarily a loss of meaning, it can lead to a word becoming more abstract or having a different connotation. For example, the word "meat" originally referred to any type of food, but now it specifically means animal flesh.
3. Dead Metaphor: This is a metaphor that has lost its figurative meaning and is now understood literally. For example, the phrase "kick the bucket" originally meant to kick over a bucket used to hang someone, but now it simply means to die.
4. Obsolescence: This term refers to the process of a word falling out of use and becoming obsolete. This can happen due to changes in language, technology, or culture. For example, words like "wireless" and "telegraphy" are now considered archaic.
5. Weakening: This term can be used to describe a general process of a word losing its strength or forcefulness, often through overuse or changing social norms. For example, the word "amazing" has become so overused that it has lost some of its original impact.
The specific term used will depend on the specific process by which the word lost its meaning and the degree of meaning lost.