油腻 (yóunì)
The original meaning of this word is actually 'greasy'. However, last year, one Chinese blog post was titled: “How to avoid becoming a greasy, dirty middle-aged man” became a viral hit on the internet. The article sparked controversy by listing a number of behaviors of middle-aged men which the author considered “greasy”, such as putting down younger people or being sleazy. This has inspired a lot of commentary by other netizens, who have compiled their own list of greasy behavior, also for other demographics.
An example is:
"他这行为很油腻!"
(ta zhe xing wei hen you ni)
Which means this act of his is very 'greasy'!