What does Genesis 12:11 mean?

God has promised the land of Canaan to Abram's descendants (Genesis 12:7). However, Abram's large company are forced to leave the land of Canaan, and to enter the land of Egypt, in order to escape a severe famine. It is important to read verses 11–13 together to understand the full context of the scene which unfolds. For the first time, we get a glimpse of Abram's fearfulness in spite of his belief in the promises of God.

Abram plans to tell a half-lie to the people of the land of Egypt to protect himself from harm, at his wife's expense. Abram begins here by acknowledging to Sarai that she is a woman of great beauty. In the next verse, he will tell her why that's a problem. His concern seems to be that those interested in taking Sarai as their own wife might choose to kill her husband in order to make her available.