Dota has a lot of lingo, and players have their own set of short hand phrases. This is immensely confusing at first. This is not 100% comprehensive, but here are some things you will hear.
b: Short for “back” which means “GET BACK RETREAT YOU WILL DIE IF YOU STAY THERE.”
Burst damage: a lot of damage suddenly given out at one time.
BKB: Short for Black King Bar, an item that makes a hero magic immune (which means you can't cast spells on them. There are some exceptions, but they will still take no damage.)
cc: short for "crowd control" which refers to how to disable heroes in team fights. If a hero has good cc, that means they can easily use their abilities to take people out of a fight.
Creep line: Refers to the line of creeps whacking on each other
Creep wave: refers to a batch of creeps that come out of the base
Crow: short for the courier, specifically flying courier. If someone says “recrow” that means they accidentally (or purposefully) changed its route from you.
Deny: refers to killing your own creeps or towers, resulting in the enemy not getting experience or money. You can only do this if your creep or tower is below 10% HP.
Farm: as a noun, refers to how much gold and experience someone has. As a verb, it means to obtain gold and experience.
Fat: refers to a character who is at a high level or has obtained very powerful items
Feed/feeding/fed: refers to heroes dying to each other. If you die multiple times to some hero, that means you are “feeding” that character gold and experience, which results in them being “fed” or “fat.”
Furion: refers to the hero Nature’s Prophet
Gank: refers to killing or attempting to kill an enemy hero by surprise.
Hard carry: refers to carries that perform extremely well once at a sufficient level and with enough items
Jungling: taking down neutral creeps in the jungle
Mega creep: super creeps that appear when barracks have been destroyed
Mek: short for Mekanism, a healing item. If you are a support, you will probably be making this.
Mis/miss/mia: Short for “missing” which means the enemy cannot be seen in their lane and may be coming to another one to attack your teammates.
Naix: refers to the hero Lifestealer.
Nuke: a powerful spell that does a lot of damage
OOM: short for “out of mana” which means they can’t cast spells
Pipe: short for Pipe of Insight, an item that reduces magic damage
POTM: refers to the hero Mirana (Priestess of the Moon)
Pulling: refers to attacking creeps in the jungle, running to the lane, and having your creeps fight the neutral creeps. This causes your creep wave to be distracted, which allows you to be closer to your tower or deny the enemy experience.
Racks/Rax: short for “barracks”
Re: short for “return” which means an enemy previously thought missing has returned to their lane
Rhasta: refers to the hero Shadow Shaman
Rosh: short for Roshan, the powerful enemy creep near the middle of the map. Once killed, he drops an item that can revive a single hero, and everyone gets a lot of gold and experience. It takes the entire team to defeat him, so don’t rush in there by yourself. When people say “we should Rosh” or “they’re Roshing!” that means attacking Roshan.
Silence: a status effect that results in you being unable to cast spells
Sheepstick: refers to the Scythe of Vyse, which turns heroes into a defenseless pig (a sheep in Dota 1). If you play an intelligence hero, you will hopefully make one of these if you can afford it.
ss: Short for “missing” which means the enemy cannot be seen in their lane and may be coming to another one to attack your teammates.
Stacking: a technique where you attack a neutral creep camp when the clock ends with :53, and run away. They will chase you, but since it will turn :00 before they return, another creep camp will spawn in its, but the first creeps will return. This is useful for allowing your carries to farm.
Stun: a move that completely immobilizes the enemy. These are extremely important in every game.
Team fight: a fight where many if not all players on both teams are engaged. If someone says “we have no team fight” that means you don’t have a hero that has spells that excel in these situations.
TP: short for teleport i.e. from a teleport scroll
Truesight: You can see invisible enemies or objects. Towers have this, and some items give you this as well.
Wards/warding: refers to observer wards and placing them on the map