Collimated

Low-mass objects have much more collimated flows than high mass sources.

Source: wiktionary

2008 May, A. M. Soderberg, et al., An extremely luminous X-ray outburst at the birth of a supernova, Accepted draft, page 3, Wolf-Rayet stars are also argued⁹ to give rise to gamma-ray bursts, a related but rare class of explosions characterized by highly-collimated relativistic jets.

Source: wiktionary

Although the most collimated outflows look very much jet-like at the highest velocities, their behavior is much more classical at lower speeds.

Source: wiktionary

Closing the aperture results in more collimated light, as only light traveling in the right direction can make it through the smaller opening.

Source: wiktionary