Ungainly usually describes someone or something moving in an awkward or clumsy way, or the awkward, clumsy movements themselves. It can also describe an object that is difficult to handle (especially because of being large or heavy), or someone or something that has an awkward appearance.
While seals are ungainly on land, they are beautifully agile swimmers.
Getting the ungainly couch up the stairs was a real chore.
The creature is large and ungainly.