Green’s Dictionary of Slang

beagle v.2

[? SE beetle off]

to leave.

Online Sl. Dict. [Internet] beagle v 1. to leave in a hurry; not running, but quickly and quietly so as to not attract attention. Usually used in the past tense because the person in question has already ‘beagled.’ (‘After realizing she was at the party, he decided to beagle.’).