A hunk is a well-built sexually attractive man. You'll find similar descriptions in dictionaries and various sites. Well-built as in muscular - not necessarily a bodybuilder, definitely muscled and lean with an cute, handsome or rugged but attractive face. In other words, hot and good looking.
Hunks don't have to be bodybuilders or extremely muscular - just muscular enough to give definition and a masculine shape. You may notice them at the gym because they are often the sexiest guys there and they work to chisel their masculine form.
But there are muscle hunks, too. These are bodybuilders who are good looking as well and have the look that both men and women find sexy. Guys like Mark Wolff epitomize the term "muscle hunk" with incredible good looks, plenty of hard-earned muscle plus a very powerful sexuality.
Somehow lately an awful lot of sites out there that don't really offer what most of us would consider a hunk at all have gotten into the act. Guys who know a hunk is something good, but they're not sure what, use the word on their tours hoping to sell more memberships.
Let's be real - a hunk is a guy who most of us notice. Their presence in a room makes people look. A hunk looks good, has a muscled shape and is just plain hot. We know 'em when we see 'em and we love seeing as many of them as possible!