Dilution is the reduction in shareholders' equity positions due to the issuance or creation of new shares. For example, if you own 10 of the 100 shares, you own 10% of the company. If the company issues another 100 shares you own 10 shares of 200 shares, thus 5% instead of the initial 10%. You share in the company is diluted.
Selling your shares, which results in less shares in the company, is not a dilution of your shares.