This refers to the fast- or rapid-acting insulin diabetics use at mealtimes. Doing a curve on anyone will indicate how blood glucose levels rise after eating. This is called a post-prandial or post-meal spike; in humans, it commonly begins about 2 hours after food. The pancreas of a non-diabetic simply produces more insulin to handle the additional glucose.
Bolus insulin can also be referred to as "mealtime insulin" because it is meant to handle the glucose increase from food. Bolus differs from booster or corrective insulin because it is part of the daily insulin routine--given slightly before or just after meals, depending on the insulin used.
Cats don't need bolus insulin as a rule. Giving them an injection of an appropriate basal insulin at mealtimes generally takes care of food spikes. Caregivers with pets that have strong post-prandial or post-meal spikes often manage those spikes better by using a Lente insulin instead of an insulin like NPH, being 30% semilente (a short-acting insulin) and 70% ultralente (a long-acting insulin), handles the spike with its short-acting semilente portion.
Some caregivers also manage post-meal spikes through changes in the pet's dietary regimen, for example by feeding several small meals during the day rather that a few large meals.
With dogs, opinions differ. Some caregivers use the methods above with success, others believe that a basal/bolus regime (see Tight regulation) is safer and more effective for their dogs. Since dogs are more prone to blindness and certain other complications of hyperglycemia, and in general have higher post-prandial spikes, it may be important to regulate them more tightly than cats.