Answer
Geometric with a common ratio of $6$.
Work Step by Step
Check if there is a common ratio by diving two consecutive terms:
$\dfrac{-6}{-1}$ $=6$;
$\dfrac{-36}{-6}$ $=6$ ;
$\dfrac{-216}{-36}$ $=6$.
The ratio is constant so this is geometric.The common ratio is $6$