#2: The use of acronyms like BRB, ROFL, OMG and WTF in spoken conversation as opposed to actually laughing, showing disbelief etc.
#3: A word, phrase or acronym that is so ingrained in someone's head, that they use without thinking if it's appropriate or even makes any sense at all.
Example of #2: A person who uses 'ROFL' when speaking to them instead of actually laughing. This is a communication crutch because they either don't get the joke, don't know how to laugh or are just condescending assholes.
Example of #3: "I'm pretty sad, my grandma just died"
"That sucks lol"
"Why are you laughing about my grandma dying?"
"Sorry about that lol"
No matter what you say, this person has the communication crutch 'lol' and will automatically type it in every response.