noun
shirker; lazy person; slacker
Colloquial and mildly derogatory term for someone who habitually avoids work or responsibility. Often used in workplace or school contexts.
彼はいつも仕事をサボる横着者だ。
He's a shirker who always slacks off at work.
あの横着者に任せると、
If we leave it to that slacker, we'll miss the deadline again.
サボり魔 is slangier and focuses on the act of skipping work or school, whereas 横着者 implies a character trait of laziness and irresponsibility.
Compound of 横着 (おうちゃく, 'laziness, shirking') and 者 (もの, 'person'). The exact derivation of 横着 is uncertain, but it is associated with the idea of 'lying down' or 'taking the easy way out'.