Intrusive is an adjective, which means a special quality of a person who, with his mild, cunning or prudent behavior, is able to gain favor with others or arouse their trust and sympathy. This definition can be used in literature in both negative and positive ways. As a rule, authors resort to this adjective in order to emphasize some psychological qualities of a person: his secretiveness or, on the contrary, benevolence.
Smarmy is a definition that suits people smart and observant. As a rule, the authors, using this term, mean their ability to charm others with good or unkind intent. Usually in fiction, this word can be found in the descriptions of people acting on the sly.
This adjective is applicable to those characters who hide their intentions from others, but on the other hand they are trying in every way to gain confidence in them and to know their secrets. In this case, the adjective in question is used with a negative nuance. So ingratiating is a word that most often means in a work of art a person who is mind.
Other meanings of the word
The definition in question, however, may also have a figurative meaning. In such cases, the authors resort to it when they want to show something that makes an extremely pleasant impression, something that penetrates the soul and leaves pleasant memories. In these insinuating examples, this is a concept that has a positive meaning. Usually it is used to describe the voice of a person or other sound phenomena (music, songs, etc.).
Also, this definition is applicable to the description of smells, since in this case the word in question means something that makes you drunk, makes a pleasant impression on a person's feelings, his emotions.
So, the meaning of the word “ingratiatingly” can be different. Most often it is used in fiction when describing the characters, as well as natural phenomena or any sound effects. This adjective has an emotional tinge, since, depending on the context of the work, it allows the writer to understand his character, in relation to which he used this definition. In descriptions of nature, it enhances the meaning and visibility of the depicted phenomena.