Acronym for "Hammered Dog Ass". Completely lacking in aesthetic merit, extremely ugly, displeasing to the eye and viscera. The resulting visual summary of an already homely subject after a losing impact with something large, heavy and iron.
May also be used to express feeling under the weather, i.e. "I feel like____."
M: That girl was pretty cute last night man, it's a shame I wasn't able to go home with her.
B: On the contrary, she had the beak of a falcon, no chin, and a dusky mustache. She looked like HDA, (Hammered Dog Ass.)
November 10, 2008