I frequently stumble upon the term "lightweight crypto". It tends to be used is a for special algorithms that use less resources, for constrained systems. Yet, it's somewhat unclear to me where to draw the line between "regular algorithms" and "special algorithms".
Since even some well-known cryptographers use the term "lightweight cryptography", I assume there must be an official, generally accepted definition for it. Yet, I fail to find it... since every source I trace down seems to define the term a bit different. For example: some even put AES into the basket when they were able to make it run on some limited-abilities piece of hardware, while others explicitly exclude AES from the lightweight crypto group. Same for ChaCha20, etc.
To avoid confusion, knowing the official definition (and maybe even having a reference to point to) would definitely help.
What is the official, generally accepted definition of "lightweight crypto"? And where (reference) is it defined?