ponderous

slow and laborious because of weight

• “the heavy tread of tired troops”
• “moved with a lumbering sag-bellied trot”
• “ponderous prehistoric beasts”
• “a ponderous yawn”

having great mass and weight and unwieldiness

• “a ponderous stone”
• “a ponderous burden”
• “ponderous weapons”

labored and dull

• “a ponderous speech”