He felt lethargic after staying up all night.

He moved lethargically, dragging his feet along the ground.

He felt lethargical after staying up all night.

Her lethargicness prevented her from completing her daily tasks.

She is lethargizing on the couch.

He lethargized after a long day at work.

He lethargizes on the couch all day.

The hot weather always lethargizes me.

He was diagnosed with a lethargick condition.

Encephalitis lethargica is a rare neurological disorder that causes extreme sleepiness.