negligent; careless; halfhearted; irresponsible
Describes an attitude or action that is sloppy, lacking proper care, or done without commitment. Often used for work, attitude, or responses that are offhand or reckless.
I was disappointed by his negligent way of working.
You can't succeed with such a halfhearted attitude.
Standard spelling; the most common written form.
Alternate kanji spelling using 遣り; less common but still encountered.
Irregular kanji usage; 槍 is a phonetic substitute, not semantically related.
From 投げ遣り, the noun form of 投げ遣る, “to throw aside.” The physical sense of casting something away developed into the figurative sense of acting carelessly or without commitment.