"In the weeds" is a slang term I only encountered after moving to Florida. My first encounter with it involved a waitress/bartender I was friendly with at a local watering hole. Noticing she was rushing about and barely had time to greet me with a "hello," less our usual banter, I asked her if everything was "okay."
Foolish me. Although I had been paying attention and noticed the bar was much busier than normal, I mistook her lack of enthusiasm for a personal issue.
"I'm sorry, hun, I've been in the weeds all night."
Well, being the type of person who thinks there is always some kind of underlying message in everything people say, I puzzled over her comment while sipping my beer. Was this a kind of code I was meant to decipher in order to understand her true feelings for me? After all, I had a giant crush on her based upon seeing her in my dreams for three years before ever meeting her. Foolish me.
"I've been in the weeds so long I haven't even had a chance to sneak out for a cigarette."
Uh huh! Obviously she was trying to tell me that she wanted me to sneak outside and smoke with her so she could tell me her problems. Brilliant deduction? No, just foolishness brought on by the fact that I was mesmerized by her incredible beauty and the fact that she wore black shorts so well.
Finally, in a stroke of mad genius, I stopped another of the waitresses and asked her if she knew what her associate might mean by "in the weeds." Looking at me as the lovable idiot I liked to portray myself as, she shook her head.
"It just means she is so busy that she can't think straight.
Try thinking straight when you are trying to remember ten orders and fifteen people are yelling at you because their glasses are empty.
In the weeds is a state of mind.
It is like going into a zone.
The weeds can strangle you if you're not careful."
Thanks to Mike1024 for pointing out the fact that I used this term in an old writeup and never defined it. | 
