HOUSTON—More than three decades after the song was a chart-topping smash and became an instant classic-rock staple, ZZ Top finally revealed to fans Tuesday the meaning behind its iconic hit “Legs.” “People have been coming up with all these crazy interpretations for 30 years, so we’ve finally decided to just come out and say that the song’s about a woman’s sexy legs and how much they make us want her sexually,” said lead vocalist Billy Gibbons, acknowledging that spelling out the meaning of “Legs” might take away from its longstanding mystique. “If the song means something else to you, that’s still cool, but there were lots of people who wanted to know what we were driving at.” Gibbons went on to say, however, that most of ZZ Top’s songs, such as the anti-apartheid anthem “Tush,” were pretty straightforward.