Here the front end is anchored, often because the fomc is on hold, while the 10-year and 30-year sell off. Causes include heavy quarterly-refunding issuance, a rising term-premium, foreign selling, or an inflation scare at the long end.
Bear steepening is hostile to equities, particularly long-duration growth names, because the discount rate on distant cash flows rises without any offsetting growth story.
Example: the 2-year is flat at 4.50% while the 30-year rises from 4.30% to 4.75%. Nothing changed about Fed policy, but 30-year mortgage rates and corporate borrowing costs jumped.
Related: bull-steepener, bear-flattener, term-premium, curve-steepener