Heavily laden, as if to creak under the strain.
That groans.
A low sound associated with extended suffering, sorrow, and toil.
Severe, intense, hard.
Sharp, snithy, piercing.
Showing clever resourcefulness in practical matters.
Streetwise, street-smart.
Knowledgeable, intelligent, keen.
Nigh accurate.
Artful, tricky or cunning.