This is the 896th most frequent Russian word.
заключил
"Concluded" or "entered into."
In this sentence, 'заключил' means 'entered into' or 'concluded' in the context of forming an agreement or contract.
Он заключил с партнёром выгодный контракт.
He entered into a profitable contract with a partner.
In this case, 'заключил' implies the physical action of locking or securing something, specifically a door.
Заключив дверь, он почувствовал себя в безопасности.
After locking the door, he felt safe.
Here, 'заключил' refers to the act of encapsulating or enclosing an idea conceptually within an expression.