rock solid

rock solid
ˌrock-ˈsolid , rock solid adjective
1. rock-solid things can be depended on and trusted not to change:
    a rock-solid guarantee
2. very hard and not likely to break

rock solidBrE /ˌrɒk ˈsɒlɪd/ 🔊NAmE /ˌrɑːk ˈsɑːlɪd/ 🔊 adjectivethat you can trust not to change or to disappear 稳固的；坚实的；可信赖的◆The support for the party was rock solid. 这一政党得到了坚定的支持。🔊🔊extremely hard and not likely to break 坚硬的；不会碎的