What is the definition of a opening adjective?

There isn't a grammatical term called "opening adjective." It seems like you're trying to describe a specific kind of adjective, but the term isn't standard.

Here's what you might be thinking of, and how to describe it:

1. Adjectives that start a sentence:

This is grammatically correct, but there's no special term for it. For example:

* Beautiful flowers bloomed in the garden.

* Tired from the long day, she went to bed early.

2. Adjectives used as introductory phrases:

These are phrases starting with adjectives that modify the noun that follows. These are also not a specific grammatical term.

* Happy with her new job, she started to feel more confident.

* Tired of waiting, he decided to leave.

3. Adjectives in a specific context:

Maybe you're looking for a specific usage of adjectives in a particular type of writing or genre. If you provide more context, I can help you find the appropriate term or description.

To get more specific help, tell me:

* What type of writing are you working with? (e.g., poetry, fiction, technical writing)

* What is the specific sentence or passage that you are interested in?

* What makes you think this adjective is "opening"?

With more information, I can help you understand the function and meaning of the adjectives you're looking at.