Cross Road Sign
MUTCD W2-1
A four-way intersection is ahead; watch for cross traffic.
What it looks like
A yellow diamond warning sign with a black plus-shaped symbol representing a four-way intersection ahead.
When you'll see it
It stands in advance of a crossroad where another road crosses yours, often where the intersection is hard to see until you are close.
What to do
Slow down, watch for traffic entering or crossing from either side, and be prepared to yield or stop as required.
Related signs
Source: Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition — FHWA.