ziellos
aimless
Without a specific destination, plan, or clear direction in a movement or action.
Nach der Arbeit spazierte er ziellos durch die Straßen der Stadt.
After work, he wandered aimlessly through the city streets.

aimless
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aimless
Without a specific destination, plan, or clear direction in a movement or action.
Nach der Arbeit spazierte er ziellos durch die Straßen der Stadt.
After work, he wandered aimlessly through the city streets.

The word consists of the noun 'Ziel' (goal/destination) and the ending '-los' (-less), which means 'without'. 'Ziellos' (aimless) therefore literally means 'without a goal'. This structure is also found in words like 'hoffnungslos' (hopeless) or 'sinnlos' (pointless).
Ein Leben ohne Träume kann sich ziellos anfühlen.
A life without dreams can feel aimless.
'Ziellos' (aimless/aimlessly) can stand as an adjective before a noun or as an adverb describing a verb. As an adverb, it remains unchanged in the sentence.
Es war ein zielloser Spaziergang ohne festen Plan.
It was an aimless walk without a fixed plan.
The literal meaning (without direction) is usually used with verbs of movement such as 'gehen' (to go/walk), 'fahren' (to drive/travel), or 'umherirren' (to wander around). The figurative meaning (without a life plan) often appears with verbs such as 'sich fühlen' (to feel), 'sein' (to be), or 'wirken' (to seem).
Das Schiff trieb ziellos auf dem offenen Meer.
The ship drifted aimlessly on the open sea.
In the literal meaning, 'ziellos' (aimlessly) is often combined with the adverb 'umher' (around/about) to emphasize undirected movement. Typical verbs are 'umherlaufen' (to walk around), 'umherfahren' (to drive around), or 'umherirren' (to wander around).
Er lief stundenlang ziellos in der fremden Stadt umher.
He walked around aimlessly for hours in the unfamiliar city.
blue
'ins Blaue' and 'ziellos' both describe a situation where there is no clear goal or fixed direction. 'Ins Blaue' usually appears in fixed expressions and often suggests spontaneous action, for example with a trip or a guess. 'ziellos' describes a movement, action, or even a feeling about life without direction more directly. If someone simply starts walking or does something without orientation, 'ziellos' fits. If you want to emphasize that someone starts without a fixed plan, 'ins Blaue' sounds more natural.

Nach dem Streit lief Lena ziellos durch die Stadt.
After the argument, Lena wandered aimlessly through the city.
In den Ferien sind sie ohne Hotelbuchung ins Blaue losgefahren.
During the holidays, they set off without a hotel booking and no fixed plan.