Boll (noun)

1. A rounded seed-vessel of certain plants, especially cotton and flax.
2. A rounded knob or protuberance on an object, such as a tree or a piece of machinery.

Origin:

The word boll is derived from the old english word "bolla" which means "a rounded seed-vessel of a plant".

Examples:

1. The cotton bolls were ready to be picked.
2. The boll weevil is a pest that feeds on the cotton bolls.
3. The boll on the tree was a sign that it was diseased.
4. The boll on the machine was a sign that it needed to be serviced.
5. The boll was filled with seeds, ready to be harvested.