a general direction in which something is developing or changing

an upward trend in sales and profit margins

a fashion

the latest trends in modern dance

a topic that is the subject of many posts on a social media site or application within a short period of time

for more than 20 days in a row, most of the top Twitter trends were Olympics-related

change or develop in a general direction

unemployment has been trending upwards

(of a topic) be the subject of many posts on a social media site or application within a short period of time

I've just taken a quick look at what's trending on Twitter right now

I'd noticed that this meme was trending on Facebook, so I created my own version