subs. (old).A slender person; a LAMP-POST (q.v.): also a simile of delusive strength.
1614. Terence in English. These therefore they diet, albeit that the nature of the gyrles is to be ful and fatte; neverthelesse by this, their diligent dressing and trimming of them, they make them as small as a BULRUSH; and hereupon it falls out that young men are enamoured of them.
TO SEEK A KNOT IN A BULRUSH, verb. phr. (old).To cavil; to find difficulties where there are none: also (in sarcasm) TO TAKE AWAY EVERY KNOT IN A BULRUSH.