Diligent and thorough in inquiry or investigation:
— A searching investigation of their past dealings.

synonyms: inquisitory, probing.

Roget 739: severe; strict, hard, harsh, dour, rigid, stiff, stern, rigorous, uncompromising, exacting, exigent, exigeant^†, inexorable, inflexible, obdurate, austere, hard-headed, hard-nosed, hard-shell [U.S.], relentless, Spartan, Draconian, stringent, strait-laced, searching, unsparing, iron-handed, peremptory, absolute, positive, arbitrary, imperative; coercive etc. 744; tyrannical, extortionate, grinding, withering, oppressive, inquisitorial; inclement etc. (ruthless) 914.1; cruel etc. (malevolent) 907; haughty, arrogant etc. 885; precisian^†.    ... show more

Roget 830: causing pain, hurting etc. v.; hurtful etc. (bad) 649; painful; dolorific^†, dolorous; unpleasant; unpleasing, displeasing; disagreeable, unpalatable, bitter, distasteful; uninviting; unwelcome; undesirable, undesired; obnoxious; unacceptable, unpopular, thankless.    unsatisfactory, untoward, unlucky, uncomfortable.    distressing; afflicting, afflictive; joyless, cheerless, comfortless; dismal, disheartening; depressing, depressive; dreary, melancholy, grievous, piteous; woeful, rueful, mournful, deplorable, pitiable, lamentable; sad, affecting, touching, pathetic.    irritating, provoking, stinging, annoying, aggravating, mortifying, galling; unaccommodating, invidious, vexatious; troublesome, tiresome, irksome, wearisome; plaguing, plaguy^†; awkward.    importunate; teasing, pestering, bothering, harassing, worrying, tormenting, carking.    intolerable, insufferable, insupportable; unbearable, unendurable; past bearing; not to be borne, not to be endured; more than flesh and blood can bear; enough to drive one mad, enough to provoke a saint, enough to make a parson swear, enough to gag a maggot.    shocking, terrific, grim, appalling, crushing; dreadful, fearful, frightful; thrilling, tremendous, dire; heart-breaking, heart-rending, heart-wounding, heart-corroding, heart-sickening; harrowing, rending.    odious, hateful, execrable, repulsive, repellent, abhorrent; horrid, horrible, horrific, horrifying; offensive.    nauseous, nauseating; disgusting, sickening, revolting; nasty; loathsome, loathful^†; fulsome; vile etc. (bad) 649; hideous etc. 846.    sharp, acute, sore, severe, grave, hard, harsh, cruel, biting, caustic; cutting, corroding, consuming, racking, excruciating, searching, grinding, grating, agonizing; envenomed; catheretic^†, pyrotic [Med.].    ruinous, disastrous, calamitous, tragical; desolating, withering; burdensome, onerous, oppressive; cumbrous, cumbersome.    ... show more

Polish: wnikliwy, dociekliwy

Having keenness and forcefulness and penetration in thought, expression, or intellect:
— Searching insights.

synonym: trenchant.

Polish: przenikliwy

Exploring thoroughly.