Webster's Revised Unabridged Dictionary · 1913

Slapdash

Slapdash , adverb

[Slap + dash.]

1.
In a bold, careless manner; at random. [Colloquial]
2.
With a slap; all at once; slap. [Colloquial] — Prior

Slapdash , transitive verb

To apply, or apply something to, in a hasty, careless, or rough manner; to roughcast; as, to slapdash mortar or paint on a wall, or to slapdash a wall. [Colloquial] — Halliwell