Two-and-a-half meal person refers to those people who break the routine of three meals a day and always delay at least one meal (and then they don't eat right) because they're either too busy at work, or indifferent about eating.
Those people usually have breakfast on their way to the office or have a brunch at a later time. Their lunch often takes place at desk and may repeatedly be interrupted by business calls, and dinner is sometimes cancelled because of extra work or weight issue. Three square meals eaten on time is an important Chinese health tradition. But these people consider dining more of a burden than a pleasure.