Г266
ОЧЕРТЯ ГОЛОВУ
collVerbal AdvInvaradvfixed WO 1. \Г-266 броситься, кинуться и т. п. (to rush into sth. , do sth. ) recklessly, thoughtlessly: (rush (plunge, throw o.s. etc)) headlong (into sth. )
(throw
o.s. etc) rashly (into
sth. )throwing caution to the winds.
2. бежать, мчаться и т. п. — (to run, race) very quickly, impetuously
at breakneck speed
for all one is worthlike a bat out of hell.
Apparently, a blend of сломя голову (which influenced the meaning) and очертить кругом (which refers to the old custom of drawing a line around oneself or another person in order to obtain protection from evil forces).
the corresponding modern form is the perfective verbal adverb очертив.