Sensuousness simply means that which relates to the senses. It's very much a hallmark of Keats's poetry. A great example occurs in "Ode to a Nightingale" where Keats describes in sumptuous detail the intoxicating effect that drinking wine has upon him:

O for a beaker full of the warm South
Full of the true the blushful Hippocrene.

Although the sense of sight may not be very prominent in this particular poem—nightfall is approaching, after all—the sense of smell most certainly is. As he sits in a garden amidst the encroaching gloom, Keats can smell the pungent perfume of many different flowers:

I cannot see what flowers are at my feet,
Nor what soft incense hangs upon the boughs,
But, in embalmed darkness, guess each sweet.

Arguably the most explicitly sensuous of all Keats's works is the "Ode to Autumn" in which all five senses are stimulated by this "season of mists and mellow fruitfulness." Here, Keats delights in the gorgeous sight of ripe flowers, fruit, and "moss'd cottage-trees." Then there is the sweet music of nature that instantly appeals to his ear:

The redbreast whistles from a garden-croft.