Pistol and pistil are easily confused words: change just one letter adn you have a whole new word. The spell-check of most word processing software programs would not catch a slip-up among these words. As long as it’s a word and it is spelled correctly, spell-check keeps on scanning the document.
Pistol is a noun. It means a handgun with a short barrel intended to be fired using just one hand. Rifles, muskets, and older models of guns require two hands for steadiness while firing at game or the enemy.
Pistil is a noun. It is the female part of the flower that extends from the center, on lilies its the largest protrusion from the center, and it has a three-lobed knob at its top.
The following sentence uses both words correctly:
Odd things show up in military journals and trunks, like botanical drawings, proving that some drafted soldiers were more interested in pistils than pistols.
[Thanks to Lovelitter blog for a source for this sentence.]