Something that prevents, hampers, or hinders.

“Age is often a handicap.”

An allowance of a certain amount of time or distance in starting, granted in a race (or other contest of skill) to the competitor possessing disadvantages; or an additional weight or other hindrance imposed upon the one possessing advantages, in order to equalize, as much as possible, the chances of success.

“A handicap in chess often involves removal of the queen's rook.”

(sometimes considered offensive) The disadvantage itself, in particular physical or mental disadvantages of people.

To encumber with a handicap in any contest.

(by extension) To place at disadvantage.

“The candidate was handicapped by her lack of experience.”

To estimate betting odds.

“Grandpa Andy would buy the racing form the day ahead of time so he could handicap the race before he even arrived at the track.”