bad top

bad top

[′bad ‚täp]
(mining engineering)
A weak roof in a coal mine; sometimes develops following a blast.
References in periodicals archive ?
Controversy is the word of the year as Miley Cyrus's twerking, NSA spying, zombies, selfies and Breaking Bad top Yahoo's most searched terms in 2013.
That's not a bad top four, and that doesn't even include Chara and Marc Savard, who are decent aces in the hole.
We saw a number of nice-looking cookstoves, some priced higher than our budget, many sadly sitting outside in the weather with rusted out ovens, bad grates, bad tops.