Synonyms for heavy

weighty

Describing abstract and physical things, often signifies seriousness; example: a weighty tome, discuss weighty issues.

unwieldy

Refers to things that are difficult to handle, whether abstract or physical; example: an unwieldy bureaucracy or object.

cumbersome

Typically used for machines and equipment that are difficult to handle; also applies to systems and structures; example: a cumbersome weapon.

burdensome

Usually describes abstract things that impose a heavy load or obligation; example: a burdensome duty.

ponderous

Characterized by slow and clumsy movement or style, often excessively serious; example: a ponderous thesis.

lumbering

Usually describes physical things suggesting heavy movement; example: a lumbering truck.