Stock option dilution is when a company issues new stock to people like employees, investors, and executives. The stock options are like pieces of a pie: when the company issues more pieces, each piece is worth less. If you own 1 piece of the pie before, and the company issues 2 more pieces, your piece is now only 1/3 of the pie, instead of 1/3. Dilution means that your share of the company is worth less than it was before.