It depends on the sentence. It can be an adjective or a noun.
Example of Twinkling as an Adjective:
Patrons can walk or drive through an amazing array of twinkling lights and sparkling displays.
Example of Twinkling as an Noun:
Some of you believe in possessions, well the knowledge in a twinkling of the eye did not take place here then did it.
See the related link.
adverb
what part of speech is beneath
i want to know what part of speech is camping
The part of speech is a adjective
Oppose is a verb.
Twinkled
part of speech
The part of speech for this particular word is a noun.
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "explicit" is an adjective.
The part of speech for "twirl" is a verb.
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "lecturer" is a noun.
The part of speech for "indefinite" is an adjective.