A steamer used for towing ships, boats, rafts, fishing-nets, oyster-dredges, etc.(noun)
The Century Dictionary (Public Domain)
Use "steam-tug" in a sentence
"Musing in this way, and taking a last look at the green fields of old England, soaking with rain, and comfortless though they then looked, I soon became aware that we had weighed anchor, and that a small steam-tug which had been getting her steam up for some little time had already begun to subtract a mite of the distance between ourselves and New Zealand."
"And then again: you saw that ship being towed out by a steam-tug?"
"It might be worth while, one would think, to try a small steam-tug for the conveyance of cattle from"