i Register
In some senses, cowardly is marked as archaic. Watch for register when choosing this word.
adj
Showing cowardice; lacking in courage; weakly fearful.
The cowardly rascals that ran from the battle.
1780, Edmund Burke, speech at The Guildhall, in Bristol The cowardly rashness of those who dare not look danger in the face.
adv
In the manner of a coward, cowardlily.
We will not ſteale vpon him cowardly, But giue him warning and more warriours.
I love to follow them, but not so cowardly, as my life remaine thereby in subjection.