The difference between Culm and Slack

When used as nouns, culm means waste coal, used as a poor quality fuel, whereas slack means small coal.

Slack is also adverb with the meaning: slackly.

Slack is also verb with the meaning: to slacken.

Slack is also adjective with the meaning: lax.

check bellow for the other definitions of Culm and Slack

Culm as a noun (botany):

the stem of a plant, especially of grass or sedge

Slack as a noun (uncountable):

Small coal; coal dust.
Slack as a noun (countable):

A valley, or small, shallow dell.
Slack as a noun (uncountable):

The part of anything that hangs loose, having no strain upon it.

Examples:

"the slack of a rope or of a sail"
Slack as a noun (countable):

A tidal marsh or shallow, that periodically fills and drains.

Slack as an adjective:

Lax; not tense; not hard drawn; not firmly extended.

Examples:

"a slack rope"
Slack as an adjective:

Weak; not holding fast.

Examples:

"a slack hand"
Slack as an adjective:

Remiss; backward; not using due diligence or care; not earnest or eager.

Examples:

"slack in duty or service"
Slack as an adjective:

Not violent, rapid, or pressing.

Examples:

"Business is slack."
Slack as an adjective (slang, West Indies):

vulgar; sexually explicit, especially in dancehall music

Slack as a verb:

To slacken.
Slack as a verb (obsolete):

To mitigate; to reduce the strength of.
Slack as a verb (followed by “off”):

to procrastinate; to be lazy
Slack as a verb (followed by “off”):

to refuse to exert effort
Slack as a verb:

To lose cohesion or solidity by a chemical combination with water; to slake.

Examples:

"Lime slacks."