gravel

rock fragments and pebbles

cause annoyance in; disturb, especially by minor irritations; "Mosquitoes buzzing in my ear really bothers me"; "It irritates me that she never closes the door after she leaves"

cover with gravel; "We gravelled the driveway"

be a mystery or bewildering to; "This beats me!"; "Got me--I don't know the answer!"; "a vexing problem"; "This question really stuck me"