This was how Susannah Wesley defined "SIN" to her young son, John Wesley:

"If you would judge of the lawfulness
or the unlawfulness of pleasure,
then take this simple rule:
Whatever weakens your reason,
impairs the tenderness of your conscience,
obscures your sense of GOD,

and takes off the relish of spiritual things---
in short, whatever increases the strength and authority
of your body over your mind,
that thing is sin to you
however innocent it may be in itself.
.....Susanna Wesley [Letter, June 8, 1725]