I recently watched an interview (Hacking the American Mind) with Robert Lustig (an endocrinologist at U.C. San Francisco). His view is that society has conflated pleasure and happiness.
He defines some qualities of pleasure: short lived, visceral, involves taking, can be obtained with substances, can lead to addiction.
Happiness on the other hand is: long lived, ethereal, involves giving, cannot be obtained with substances, does not lead to addiction.
From the perspective of our brain chemistry he says that pleasure seeking stimulates the production of dopamine where as cultivating happiness increases serotonin. Increasing dopamine down-regulates serotonin so the more we engage in pleasure seeking behaviors, the less happy we become.
I think in Buddhism, sensual pleasures, or worldly pleasures equates with Lustig’s use of pleasure. These days that would include everything from drugs to food to social media. Any kind of stimulation we seek that becomes addictive. While ‘unworldly pleasures’ refers to a more refined or rarefied version of Lustig’s happiness. Some years ago I read an article on Positive Psychology where they stated that the highest form of happiness for people was found through generosity. It is interesting that this is where the Buddhist path essentially begins.
So it may be that the pleasurable feeling that lingers after a good meditation is long lived happiness and not a pleasure (using Lustig’s definitions).