I admit I was wrong about the difference between US and UK usage, but still don't think it means "dense" here, though it could, of course, mean
both dense and having a bad smell.
https://www.collinsdictionary.com/dictionary/english/rank"...
rank in British 2
(ræŋk )
adjective1.
showing vigorous and profuse growth
rank weeds
2.
highly offensive or disagreeable, esp in smell or taste
3. (prenominal)
complete or absolute; utter
a rank outsider
4.
coarse or vulgar; gross
his language was rank
...
rank in American 2
(ræŋk )
adjective1.
growing vigorously and coarsely; overly luxuriant
rank grass
2.
producing or covered with a luxuriant crop; extremely fertile
3.
strong and offensive in smell or taste; rancid
4.
in bad taste; coarse ..."