This is the 17156th most frequent Russian word.
ствола
"Stvola" (genitive case of "stvol") means "of a trunk" (tree trunk, body trunk) or "of a barrel" (gun barrel) in English.
In this sentence, 'ствол' refers to the trunk of a tree, which is the main structural component supporting its branches.
Ствол дерева был настолько широким, что его нельзя было обхватить руками.
The tree trunk was so wide that it could not be embraced with arms.
Here, 'ствол' denotes the barrel of a firearm, which is the part of the gun through which the projectile travels.
Полицейские изъяли оружие, среди которого был пистолет с длинным стволом.
The police confiscated weapons, among which was a pistol with a long barrel.
In this context, 'ствол' signifies the cylindrical shaft or tube of a pipe or similar object.