adverb
relentlessly; strictly; without mercy
Onomatopoeic/mimetic word describing a harsh, unyielding manner of scolding, training, or enforcing rules. The 'stickily' gloss is rare and likely refers to a sticky, clinging quality, but the dominant modern use is relentless strictness.
新入社員は上司にびしびし鍛えられた。
The new employee was relentlessly trained by the boss.
先生は生徒
The teacher scolded the students without mercy.