This is a term that is used in linguistics. It means a label or name for a single word is on language that stands for the word in another language. The French gloss for "cat", for example is "le chat". We say that the gloss for "cat" in French is "le chat".
A gloss may also means an expression in one language that stands for an expression in another language. For example, in English the expression, "to have an experience which is a first time for you, but feels as if you had had it once before already" is glossed in French by the words, "deja vu".
In ASL, glosses are always written in capitals. The ASL gloss for "cat" is the sign CAT. Another example for the English gloss for the ASL sign COW-IT is "to take a long time to do something, to drag something on forevers; slowpoke".
Beginning learners of ASL run the dangerous risk of confusing losses with meanings. Remember that the gloss is simply the LABEL we use to talk about the sign. It is not the meaning of the sign. A sign such as FINISH has several meanings, so do not think it means simply "finish, ended, over".
Using "Glosses" Wisely (or How Can I Stop Signing In English Word Order?"
FIRST STEP: Retrain Your Thought Processes
Begin to create conceptual thoughts before you convert them into English grammar. You are very skilled at converting your thoughts into language, but this skill also interferes with your ability to change concepts into ASL grammar. Many students of ASL fall into the trap of letting their thinking process to follow a natural, comfortable pace.
When you sign using English word order, you tend to do following three steps: 1) Identifying the CONCEPT, 2) converting the concept into English grammar structure, 3) replacing the English words with the equivalent ASL "gloss" sign. This is common conversion error for the beginner learners.
So the first thing is to learn ASL by RE-DIRECTING your thought process. You would do the following steps: 1) Consciously identifying the CONCEPT, 2) recalling the rules of ASL and 3) applying the rules to create grammatically correct ASL sentences.
This will requires lots of practice to help you developing these new skills.
SECOND STEP: Become Very Familiar with ASL Signs and Their Meaning
To convert your concepts into ASL, you need to know which signs that will best represent the concepts you wish to communicate.
Why Use "Glosses" at All?
Glosses are quite challenging, but as you know, there is no system of "written ASL". We are therefore in the unfortunate position of relying on written/spoken English to help us identify or "write" ASL signs and sentences. The most important is to not start thinking that the ASL sign is the equivalent in meaning to and English word.