1. Ingratiating in manner or speech
2. Revealing or marked by a smug
3. Excessively smooth or greasy
Think of the word Unctuous as derived from ‘Un-cute’. Now someone with a lot of oily makeup looks superficial or insincere and hence the word Unctuous.
1. His is clearly an unctuous effort to appear religious to the voters.
2. In order to please his elder brother, he indulged in unctuous praise of his work.